IRLF 


551 


GIFT  OF 

Publisher. 


EXERCISES  IN  CHEMISTRY 


SYSTEMATICALLY  ARRANGED  tfO  ACCOMPANY 

THE  SECOND  REVISED  EDITION  OF  "AN 

ELEMENTARY  STUDY  OF  CHEMISTRY" 


BY 

WILLIAM  McPHERSON 
// 

AND 

WILLIAM  EDWARDS  HENDERSON 

PROFESSORS   OF   CHEMISTRY,  OHIO   STATE   UNIVERSITY 


REVISED  EDITION 


GINN  AND  COMPANY 

BOSTON  •  NEW  YORK  •  CHICAGO  •  LONDON 
ATLANTA  •  DALLAS  •  COLUMBUS  •  SAN  FRANCISCO 


»•)  J    J*  »M  *»<**• '     i 

fj3  >  *'  v«  *  *  »ii 

>    J>  J*  ^  j"  .  *^      *  J  ^; 


COPYRIGHT,  1906,  1919,  BY 
WILLIAM  IflcPHERSON  AND  WILLIAM  E.  HENDERSON 


ALL  BIGHTS  RESERVED 
519.9 


JCfte  gtftengum 

GINN  AND  COMPANY  •  PRO- 
PRIETORS •  BOSTON  •  U.S.A. 


PREFACE 

The  exercises  contained  in  this  .  book  are  systematically 
arranged  to  accompany  the  revised  edition  of  McPherson 
and  Henderson's  "An  Elementary  Study  of  Chemistry."  It 
has  been  thought  desirable  to  include  in  the  list  a  some- 
what larger  number  of  exercises  than  will  ordinarily  be 
performed,  thus  giving  the  instructor  some  choice  in  his 
selections.  A  number  of  simple  exercises  bearing  on  -  sub- 
jects of  special  interest  to  students  of  home  economics  are 
included  under  Appendix  A.  These  have  to  do  with  simple 
tests  for  food  constituents,  detection  of  different  kinds  of 
textile  fibers,  and  similar  topics.  If  time  is  not  available  for 
the  students  interested  in  such  subjects  to  perform  these 
experiments  in  addition  to  the  regular  ones^  the  instructor 
may  find  it  possible  under  the  circumstances  to  make  certain 
substitutions  that  will  appeal  to  his  judgment. 

While  the  experiments  selected  cover  a  wide  field  and 
are  believed  to  illustrate  the  general  topics  included  in  the 
presentation  of  an  introductory  course  in  chemistry,  never- 
theless they  may  be  performed  with  simple  apparatus  and 
with  chemicals  that  are  readily  available.  Detailed  infor- 
mation in  regard  to  the  apparatus  and  materials  required  for 
performing  the  experiments  will  be  found  in  Appendix  B. 

It  is  no  longer  necessary  to  emphasize  the  importance  of 
laboratory  work  as  a  part  of  the  course  in  elementary 
chemistry,  since  it  is  universally  admitted  that  laboratory 
experience  is  essential  for  a  thorough  comprehension  of  the 
subject.  It  is  none  the  less  true,  however,  that  laboratory 

iii 


A 


work  is  of  very  doubtful  value  unless  carefully  directed  by 
an  experienced  teacher  toward  some  definite  end.  It  is  in 
the  hope  of  aiding  such  a  teacher  that  this  exercise  book 
has  been  prepared. 


IV 


CONTENTS 

EXERCISE  PAGE 

1.  The  Metric  System 1 

2.  The  Bunsen  Burner ;  Manipulation  of  Glass  Tubing     .     .  2 
.  3.  Some  Preliminary  Manipulations 6 

4.  A  Study  of  Some  of  the  Changes  taking  Place  when  a 

Substance  Burns 9 

5.  Chemical  Action ;  Elements,  Compounds,  Mixtures  ...  11 

6.  Collection   of   Gases ;    Preparation   of  Oxygen    from   (a) 

Mercuric  Oxide,  (6)  Sodium  Peroxide •     .  12 

7.  Usual  Laboratory  Preparation  of  Oxygen;   Properties  of 

Oxygen .  14 

8.  The  Preparation  and  Properties  of  Hydrogen 17 

9.  The  Combustion  of  Hydrogen;  the  Oxyhydrogen  Blow- 

pipe   20 

10.  Oxidation  and  keduction 21 

11.  Measurement  of  Gas  Volumes 23 

12.  The  Determination  of  the  Weight  of  One  Liter  of  Oxygen ; 

also,  of  the  Percentage  of  Oxygen  in  Potassium  Chlorate  24 

13.  A  Study  of  the  Process  of  Distillation 26 

14.  The  Composition  of  Water 27 

15.  The  Preparation  and  Properties  of  Hydrogen  Peroxide      .  29 

16.  States  of  Matter 31 

17.  The  Formation  of  Charcoal  and  Coke 32 

18.  A  Further  Study  of  Carbon  . 33 

19.  A  Study  of  Carbon  Dioxide 34 

20.  Preparation  and  Properties  of  Nitrogen 35 

21.  The  Composition  of  Air 36 

22.  A  Study  of  Solutions 38 

23.  Determination  of  the  Solubility  of  Common  Salt      ...  40 

24.  A  Method  for  determining  whether  or  not  a  Given  Liquid 

is  a  Conductor  of  Electricity 41 

25.  The  Preparation  and  Properties  of  Chlorine 43 

26.  The  Preparation  and  Properties  of  Hydrogen  Chloride  and 

of  Hydrochloric  Acid 44 

V 


EXERCISE  PAGE 

27.  Sodium  ;  Sodium  Hydroxide 46 

28.  The  Properties  of  Acids,  Bases,  and  Salts 46 

29.  The  Ratio  of  Acid  to  Base  in  Neutralization 48 

30.  The  Displacement  of  Metals  from  their  Compounds      .     .  49 

31.  The  Determination  of  the  Amount  of  Hydrogen  displaced 

by  a  Definite  Weight  of  Different  Metals 50 

32.  The  Preparation  and  Properties  of  Ammonia 52 

33.  The  Preparation  and  Properties  of  Nitric  Acid    ....  54 

34.  The  Properties  of  the  Salts  of  Nitric  Acid 55 

35.  The  Preparation  and  Properties  of  Some  of  the  Oxides  of 

Nitrogen 56 

36.  Speed  of  Reactions ;  Equilibrium ;  Hydrolysis      ....  57 

37.  The  Properties  of  Sulfur  ; 58 

38.  The  Preparation  and  Properties  of  Hydrogen  Sulfide     .     .  60 

39.  The  Preparation  and  Properties  of  the  Salts  of  Hydro- 

sulfuric  Acid 61 

40.  Sulfur  Dioxide  and  Sulfurous  Acid 63 

41.  A  Study  of  Sulf uric  Acid 64 

42.  Salts  of  Sulfuric  Acid  .     .     .     *     .     .     .     .    '.     .     .     .     .  65 

43.  Hydrates;  Efflorescence    .     .     ... 66 

44.  The  Preparation  and  Properties  of  Hydrogen  Fluoride  .     .  67 

45.  The  Test  for  Hydrochloric  Acid  and  its  Salts       ....  68 

46.  The  Preparation  and  Properties  of  Bromine  and  of  Hy- 

drogen Bromide    ..............  69 

47.  The  Preparation  and  Properties  of  Iodine  and  of  Hydro- 

gen Iodide 70 

48.  How  to   distinguish   between   Chlorides,   Bromides,  and 

Iodides    .     . 71 

49.  The  Preparation  and  Properties  of  Carbon  Monoxide    .     .  72 

50.  Carbonic  Acid  and  its  Salts 74 

51.  A  Study  of  Some  of  the  Hydrocarbons 75 

52.  A  Study  of  the  Flame 76 

53.  The  Sugars 78 

54.  A  Study  of  Starch 79 

55.  The  Preparation  and  Properties  of  Common  Alcohol     .     .  80 

56.  The  Preparation  of  a  Simple  Ester 82 

57.  Phosphorus  and  its  Compounds 83 

58.  Arsenic  and  Some  of  its  Compounds 84 

59.  A  Study  of  Some  of  the  Properties  of  Antimony ....  86 

60.  A  Study  of  Some  of  the  Properties  of  Bismuth    ....  86 

61.  Compounds  of  Silicon 87 

vi 


EXERCISE  £AGE 

62.  Compounds  of  Boron 88 

63.  Colloids  and  Emulsions 89 

64.  General  Methods  for  the  Preparation  of  the  Compounds 

of  the  Metals 91 

65.  The  Compounds  of  Sodium 92 

66.  The  Determination  of  the  Weight  of  Common  Salt  ob- 

tained  by    adding    Hydrochloric    Acid    to    a    Definite 

Weight  of  Sodium  Bicarbonate 93 

67.  The  Test  for  Potassium;   the  Preparation  of  Potassium 

Nitrate 94 

68.  The  Properties  of  Ammonium  Compounds 96 

69.  Detection  of  Compounds  of  the  Alkali  Metals       ....  97 

70.  The  Preparation  and  Properties  of  Soap 97 

71.  A  Study  of  Some  of  the  Compounds  of  Calcium  ....  98 

72.  Hard  Waters  and  Methods  for  Softening  them     ....  99 

73.  Some  Additional  Experiments  with  Soap 100 

74.  The  Preparation  and  Properties  of  Bleaching-Powder    .     .  101 

75.  Magnesium  and  its  Compounds .  102 

76.  Zinc  and  its  Compounds 103 

77.  Aluminium  and  its  Compounds 104 

78.  The  Use  of  Aluminium  Sulfate  in  the    Purification  of 

Water 105 

79.  Reactions  of  Baking-Powders 105 

80.  A  Study  of  Iron,  Cobalt,  and  Nickel 106 

81.  A  Study  of  Copper  and  its  Compounds 108 

82.  A  Study  of  Mercury  and  its  Compounds 109 

83.  A  Study  of  Silver  and  its  Compounds 109 

84.  Properties  of  Tin  and  its  Compounds Ill 

85.  A  Study  of  Lead  and  Some  of  its  Compounds       ....  Ill 

86.  Detection  of  Silver,  Lead,  and  Mercury,  when  Present  in 

the  Same  Solution 112 

87.  A  Study  of  Some  of  the  Compounds  of  Manganese  .     .     .  113 

88.  A  Study  of  Some  of  the  Compounds  of  Chromium    .     .     .  114 

89.  Borax-Bead  Tests  115 


APPENDIX  A 

90.  A  Study  of  Textile  Fibers 117 

91.  The  Determination  of  the  Amount  of  Alcohol  Present  in 

an  Alcoholic  Liquid 118 

92.  The  Effect  of  Preservatives 120 

vii 


EXERCISE  PAGE 

93.  A  Study  of  Vinegar 121 

94.  Tests  for  Fats  and  Proteins 123 

95.  The  Composition  of  Flour 124 

96.  Some  Experiments  with  Milk 125 

97.  Methods  for  distinguishing  between  Butter  and  Oleomar- 

garine    126 

98.  Analysis  of  Baking-Powders 127 

99.  The  Use  of  Mordants  in  Dyeing 128 

100.  A  Study  of  Lakes ;   also  the  Effect  of  using  Different 

Mordants  with  the  Same  Dye 130 

101.  The  Detection  of  Dyes  in  Foods 131 

102.  The  Removal  of  Stains  .  132 


APPENDIX  B 

Tables  of  Constants 134 

The  Metric  System 135 

Table  of  Solubilities 137 

Treatment  of  Cuts  and  Wounds  .     .     .     .     .     .     ,     .     .     138 

Information  regarding  Apparatus  and  Chemicals     .       139-147 


Vlll 


DIRECTIONS 

A  list  of  the  apparatus  and  chemicals  necessary  for  per- 
forming the  experiments,  together  with  suggestions  as  to 
their  purchase,  is  given  in  Appendix  B.  It  is  expected  that 
each  desk  will  be  provided  with  five  of  the  most  common 
reagents  (see  Appendix,  p.  141).  When  reference  is  made 
to  any  of  these  five  reagents  under  "  materials  "  required  in 
performing  each  exercise,  it  will  be  understood  that  the  re- 
agents on  the  desk  are  the  ones  to  be  used.  Other  reagents 
used  less  frequently  should  be  placed  on  a  reagent  shelf 
available  to  all.  The  abbreviation  (R.  S.)  used  in  listing  the 
materials  necessary  for  performing  each  individual  experi- 
ment refers  to  the  reagents  on  the  reagent  shelf.  The 
abbreviation  (E)  implies  that  the  equation  for  the  reaction 
involved  in  the  experiment  is  to  be  written.  The  character  (?) 
implies  that  the  results  obtained  in  that  part  of  the  experi- 
ment are  to  be  recorded  in  the  notes.  The  word  "hood" 
signifies  that  the  experiment  is  to  be  performed  in  a  well- 
ventilated  compartment  so  that  any  poisonous  gases  evolved 
will  be  removed  at  once.  All  thermometer  readings  refer  to 
the  centigrade  scale. 

Exercises  or  parts  of  exercises  marked  with  a  star  (*) 
may  be  omitted  if  time  is  not  available  for  performing  all 
the  experiments. 


EXERCISES  IN  CHEMISTRY 

EXERCISE  1 

THE  METRIC  SYSTEM 

(See  Appendix  B.) 

Apparatus.  Graduated  test  tube  ;  balance  sensitive  to  1  eg.  and  set 
of  weights  from  50  g.  to  1  eg. ;  watch  glass ;  100  cc.  beaker. 

Materials.  Teaspoon f ul  of  common  salt ;  test  tube  full  of  dis- 
tilled water ;  nickel  five-cent  piece. 

a.  Length.  By  means  of  the  scale  (see  Appendix),  measure 
the  length  (in  centimeters)  of  various  pieces  of  apparatus 
included  in  your  outfit,  as  a  test  tube,  file,  and  blowpipe. 
What  is  the  diameter  of  your  filter  paper  ?  Finally,  estimate 
the  lengths  of  various  objects,  as  a  pencil,  a  test  tube ;  then 
measure.    Continue  until  you  can  approximate  the  lengths  of 
small  objects. 

b.  Volume.    By  means  of  a  graduated  test  tube  or  cylin- 
der, measure  (in  cubic  centimeters)  the  volumes  of  various 
test  tubes,  beakers,  and  flasks  included  in  your  outfit.    (In 
reading  off  the  amount  of  the  liquid  in  a  graduated  tube, 
always  read  from  the  lower  part  of  the  meniscus;  that  is, 
the  curved  surface  of  the  liquid.) 

c.  Weight.   Ask  the  assistant  for  instruction  in  regard  to 
the  use  of  the  balance;  then  weigh  various  small  objects, 
as  a  porcelain  crucible,  a  watch  glass.    What  is  the  approxi- 
mate weight  of  a  nickel  five-cent  piece  ? 

Accurately  balance  a  watch  glass  on  the  scalepan  (using 
either  the  weights  or  a  small  pill  box  and  fine  shot)  and 
weigh  out  on  this  exactly  5.2g.  of  common  salt. 

1 


Balance  a  small  (clean  and  dry)  beaker  on  the  scalepan; 
then  remove  it  from  .'lie  pan  and  pour  into  it,  as  nearly  as 
possible,  10  cc.  of  distilled  water  (measured  in  the  graduated 
tube  included  in  you?  laboratory  outfit).  Eeweigh,  and  note 
the  weight  of  the  water.  How  do  you  account  for  the  fact 
that  it  does  not  weigh  exactly  10g.? 

EXERCISE  2 

THE  BUNSEN  BURNER;   MANIPULATION  OF 
GLASS  TUBING 

Apparatus.  Bunsen  burner  and  wing-top  attachment,  as  shown  in 
Fig.  4  ;  hard-glass  test  tube  with  good  cork  to  fit ;  set  of  cork-borers  ; 
triangular  file  ;  round  file. 

Materials.  Wooden  splint  (1  cm.  x  12  cm.  is  a  convenient  size) ; 
white  cardboard  (10  cm.  square)  ;  soft  glass  tubing  15  cm.  in  length  ; 
glass  rod,  25  cm.  in  length. 

a.  The  Bunsen  burner.  The  Bunsen  burner  is  a  form  of 
apparatus  used  for  producing  heat  and  is  commonly  employed 
in  the  laboratory.  It  consists  of  the  tube 
A  (Fig.  1),  screwed  into  the  base  C.  The 
tube  has  two  small  openings  near  its 
lower  part.  A  small  band  B,  provided 
with  similar  openings,  fits  around  the 
lower  part  of  the  tube  in  such  a  way 
that  the  openings  of  the  tube  may  be 
closed  or  kept  open  by  turning  the  band. 
Gas  is  admitted  through  D  by  means  of 
rubber  tubing.  FlG  j 

Unscrew  the  tube  and  examine  the 
different  parts  of  the  burner ;  then  put  them  together  again 
and  light  the  gas  by  holding  a  lighted  match  4  or  5  cm. 
above  the  tube  and  turning  on  the  gas.  The  supply  should 
be  adjusted  so  as  to  give  a  flame  about  10  cm.  high.  The 
gas  flowing  through  the  tube  mixes  with  the  air  drawn  in 

2 


through  the  openings  in  the  lower  part  of  the  tube  and 
burns  with  an  almost  nonluminous  flame.  If  the  band  is 
adjusted  so  as  to  close  the  openings,  the  flame  becomes 


B 


r 


FIG.  2 


luminous.    Always  use  the  nonluminous  flame 
unless  directed  otherwise. 

Hold  a  small  wooden  splint  horizontally  in 
the  base  of  the  Bunsen  flame  for  two  or  three 
seconds  and  note  the  results.  In  the  same  way 
determine  the  relative  temperatures  of  various 
parts  of  the  flame.  Turn  the  gas  down  until 
the  flame  is  7  or  8  cm.  in  height,  then  quickly 
thrust  a  piece  of  white  cardboard,  about  1 0  cm. 
square,  vertically  through  the  center  of  the 
flame,  the  lower  end  of  the  cardboard  resting 
against  the  top  of  the  burner.  Kemove  the  cardboard  before 
it  is  ignited  and  from  the  scorched  portions  note  the  relative 
temperatures  of  different  parts  of  the  flame.  Draw  a  diagram 
to  illustrate  your  results. 

b.  To  fit  a  tube  with  stopper  and  glass  tube  as  shown  in 
Fig.  2.  In  all  operations  requiring  the  application  of  a  strong 
heat  to  glass,  the  heat  must  be  applied  gently  at  first.  Highly 
heated  glass  must  be  cooled 
slowly ;  otherwise  it  is  easily 
broken. 

From  one  of  the  lengths  of 
soft-glass  tubing  cut  a  piece 
about  15  cm.  in  length.  To  do  FlG  3 

this,  place  the  tubing  on  the 

desk  and  draw  the  edge  of  a  triangular  file  across  the  point 
at  which  you  wish  to  cut  the  glass.  After  the  glass  has  been 
scratched,  take  the  tube  in  the  hands  with  the  thumbs  placed 
near  together  just  back  of  the  scratch  (Fig.  3),  and  gently 
pull  the  glass  apart,  at  the  same  time .  exerting  a  slight  pres- 
sure with  the  thumbs.  If  the  tube  does  not  yield  readily  to 
a  gentle  pressure,  a  deeper  scratch  must  be  made.  In  the 

3 


case  of  large  tubing  it  may  be  found  necessary  to  file  a  groove 
entirely  around  the  glass.  The  edges  of  the  cut  tube  will  be 
sharp,  and  should  be  rounded  by  being  rotated  in  the  tip  of 
the  Bunsen  flame. 

To  bend  the  glass  tub- 
ing, first  heat  it  at  the 
point  where  you  wish  to 
bend  it,  in  the  lumi- 
nous Bunsen  flame  spread 
out  by  means  of  the  so- 
called  "wing-top"  burner 
(Fig.  4).  Hold  the  tube  lengthwise  in  the  flame,  gently  rotat- 
ing it  so  that  all  sides  may  be  equally  heated.  Continue  the 
heating  until  the  glass  bends  easily,  then  remove  it  from  the 
flame  and  quickly  bend  it  to  a  right  angle  B  (Fig.  2).  Great 
care  must  be  taken  to  heat  the  tube  uniformly,  otherwise  the 
bore  of  the  tube  will  be  contracted  (A,  B,  Fig.  5),  forming  a 
bend  which  is  not  only  unsightly  but  is  easily  broken. 

Next  select  a  cork  of  such  a  size  that  the  smaller  end  will 
just  enter  the  hard-glass  test  tube  A  (Fig.  2).     Soften  the 


FIG.  4 


FIG.  5 


FIG.  6 


cork  by  rolling  it  between  the  desk  and  a  block  of  wood. 
Now  insert  into  the  cork  the  glass  tube  prepared  as  directed 
above.  To  do  this,  select  a  borer  slightly  smaller  than  the 
tube.  Place  the  cork  on  the  desk  and  cut  half  through  it 
with  the  borer,  not  by  punching  but  by  rotating  the  borer 

4 


FIG.  7 


under  gentle  pressure  (Fig.  6) ;  then  reverse  the  cork  and 
bore  through  from  the  other  end.  Care  must  be  taken  to 
keep  the  borer  at  a  right  angle  to  the  top  and  base  of  the 
cork.  The  hole  should  be  straight 
and  smooth. 

The  glass  tube,  rounded  at  the 
edges,  is  now  inserted  in  the  cork 
by  a  gentle  screwlike  motion.  If 
the  hole  is  too  small  to  admit  the 
tube  when  a  gentle  pressure  is 
applied,  it  may  be  slightly  enlarged 
with  a  round  file.  Now  put  the 
cork  in  the  test  tube  and  set  the 
apparatus  aside  for  use  in  preparing 
oxygen  (Exercise  7). 

c.  To  make  glass  stirring-rods. 
Make  two  of  them,  one  about  10  cm. 
and  one  about  15  cm.  in  length.  Cut  the  rods  to  the  proper 
length  and  round  the  ends  by  heating  in  the  Bunsen  flame. 
Place  the  finished  rods  in  the  desk  for  future  use. 

*d.  To  make  a  wash  bottle.  The  student  often  will  find  a 
wash  bottle  useful  in  laboratory  work.  It  may  be  readily 
made  as  represented  in  Fig.  7.  A  500  cc.  flask  is  used. 
A  and  B  represent  soft  glass  tubes  bent  as  shown  in  the  figure. 
B  is  connected  with  the  glass  jet  D  by  a  piece  of  rubber 
tubing  C.  The  glass  jet 
D  is  made  as  follows : 
Heat  a  piece  of  soft  glass 
tubing  12  or  15  cm.  in  £ 
length  in  the  Bunsen 
flame  until  the  walls  of 
the  heated  portion  thicken  and  the  size  of  the  bore  dimin- 
ishes (Fig.  8,  A).  The  tube  must  be  constantly  rotated,  to 
prevent  the  softened  portion  from  sagging.  Now  quickly 
remove  the  tube  from  the  flame,  and,  holding  it  in  a  vertical 

5 


B 

FIG.  8 


position,  gently  pull  the  ends  apart  until  the  bore  is  of  the 
desired  size  (Fig.  8,  B).  The  glass  jet  is  then  formed  by 
cutting  the  tube  at  B  and  rounding  the  edges  in  a  flame. 

EXERCISE  3 

SOME  PRELIMINARY  MANIPULATIONS 

Apparatus.  Test  tubes  ;  glass  rod ;  2  beakers ;  funnel ;  ring  stand  ; 
evaporating  dish ;  burner. 

Materials.    Filter  paper ;  piece  of  chalk ;  2  or  3  g.  of  common  salt. 

a.  Heating  liquids  in  test  tubes.  Half  fill  a  test  tube  with 
water  and  apply  heat  until  the  water  boils  rapidly.  To  do 
this,  hold  the  test  tube  between  the  thumb  and  fingers 


FIG.  9 


FIG.  10 


FIG. 11 


(Fig.  9),  constantly  rotating  it  so  as  to  apply  the  heat  uni- 
formly. The  heat  should  be  applied  to  the  upper  portion  of 
the  liquid,  care  being  taken,  however,  that  the  flame  does 
not  strike  the  tube  above  the  level  of  the  liquid.  In  case 
the  upper  part  of  the  tube  becomes  heated,  it  may  be  sup- 
ported by  a  test-tube  holder  (Fig.  10)  or  by  a  band  of  paper 
wrapped  about  the  upper  part  of  the  tube  (Fig.  11).  The 
sudden  formation  of  vapor  sometimes  causes  the  contents 
of  the  tube  to  be  thrown  out ;  hence  care  must  be  taken  not 
to  point  the  tube  toward  anyone. 

6 


b.  Pouring  liquids  from  one  vessel  to  another.  In  doing 
this  care  must  be  taken  to  prevent  the  liquid  from  running 
down  the  side  of  the  vessel  from  which  it  is  poured.  A  glass 
rod  should  be  held  lightly  against  the  rim  of  the  vessel,  as 
, shown  in  Fig.  14.  The  liquid  will  flow  down  the  rod. 

Fill  a  beaker  with  water  and  transfer  it  slowly  to  another 
vessel  without  using  the  glass  rod  ;  repeat,  using  the  glass  rod. 

In  pouring  liquids  from  bottles  a  glass  rod  may  be  used ; 
or  the  neck  of  the  bottle  may  be  placed  lightly  against  the 
rim  of  the  vessel  into  which  the  liquid  is  being  poured 


FIG. 12 


FIG. 13 


(Fig.  13).  This  will  prevent  the  liquid  from  running  down 
the  side  of  the  bottle.  The  stopper  must  never  be  laid  down 
on  the  desk  (?).  Catch  it  between  the  fingers,  as  shown  in 
Fig.  12.  This  leaves  the  hand  free  to  grasp  the  bottle,  as 
shown  in  Fig.  13. 

c.  Decantation ;  filtration ;  solution ;  evaporation.  It  is 
often  necessary  to  separate  a  liquid  from  a  finely  divided 
solid  which  is  suspended  in  it.  This  may  be  done  by  one 
of  the  two  following  methods. 

1.  Decantation.    When   the    solid   is  heavy  and   readily 
settles  to  the  bottom  of  the  vessel  the  liquid  may  be  care- 
fully poured  off  or  decanted.    Thus  sand  suspended  in  water 
may  be  separated  from  the  liquid  in  this  way. 

2.  Filtration.    Usually,  however,  the  solid  will  not  readily 

7 


settle  or  will  do  so  only  after  long  standing.  In  such  cases  the 
mixture  is  filtered ;  that  is,  poured  on  a  filter  paper,  which 
allows  the  liquid  to  run  through  but  retains  the  solid.  To 
prepare  the  filter  paper,  fold  it  along  a  diameter  into  halves, 
then  at  right  angles  to  the  first  fold  into  quarters.  The 
folded  filter  is  then  opened  so  as  to  form  a  cone,  half  of 
which  is  composed  of  three  thicknesses  of  paper  and  the 
remainder  of  one  thickness.  Now  fit  the  cone  into  a  funnel 


FIG.  14 


FIG. 15 


of  such  a  size  that  the  paper  does  not  quite  reach  the  top. 
The  paper  must  accurately  fit  the  funnel;  if  it  does  not, 
make  it  do  so  by  varying  the  fold.  Place  the  paper  in  the 
funnel  and  thoroughly  wet  it  with  water.  After  the  water 
has  run  through,  press  the  paper  firmly  against  the  sides  of 
the  funnel  with  the  finger  so  as  to  remove  any  air  bubbles. 
The  filter  is  now  ready  for  use  (Fig.  14).-  The  process  of 
filtration  not  only  enables  us  to  separate  liquids  from  solids 
but  also  certain  solids  from  each  other.  To  illustrate  this, 
grind  a  piece  of  chalk  to  a  powder  in  a  mortar,  and  mix  the 
product  intimately  with  about  an  equal  bulk  of  common  salt. 
Place  the  mixture  in  a  small  beaker,  add  about  50  cc.  .of 
distilled  water,  and  stir  with  a  glass  rod.  (The  ends  of  the 


rod  should  be  rounded  by  rotating  them  in  a  flame,  other- 
wise the  beaker  may  be  scratched  and  broken.)  The  salt 
dissolves,  forming  a  solution.  Filter  off  the  insoluble  chalk, 
collecting  the  filtrate,  that  is,  the  clear  liquid  which  passes 
through  the  filter  paper,  in  a  beaker  (Fig.  14).  The  salt  may 
be  recovered  from  the  filtrate  by  the  process  of  evaporation. 
To  perform  this  operation,  pour  the  filtrate  into  an  evaporating 
dish,  support  the  dish  on  a  ring  stand  (Fig.  15),  and  heat 
gently.  The  liquid  may  be  made  to  simmer,  but  should  not 
actually  boil  (?).  Withdraw  the  heat  as  soon  as  the  water 
is  evaporated.  Note  the  residue  left.  Convince  yourself  that 
it  is  common  salt. 

EXERCISE  4 

A  STUDY  OF  SOME  OF  THE  CHANGES  TAKING  PLACE 
WHEN  A  SUBSTANCE  BURNS 

Apparatus.  Porcelain  crucible;  burner;  ring  stand;  pipe-stem 
triangle  to  support  the  crucible  while  being  heated  ;  pneumatic  trough 
(or  dish)  ;  wide-mouthed  bottle  or  large  beaker ;  candle. 

Materials.  2  or  3  g.  powdered  iron  ;  2  or  3  g.  granulated  tin ;  pellet 
of  phosphorus,  size  of  a  small  pea  (to  be  obtained  from  the 
instructor  when  needed);  5  cc.  limewater  (R.S.). 

a.  The  burning  of  metals.    Place  2  or  3  g.  of  powdered 
iron  in  a  procelain  crucible  and  accurately  weigh.    Now  heat 
the  crucible  (Fig.  16)  until  the  iron  begins  to  glow  (burn); 
then  withdraw  the  heat.    Does  the  iron  continue  to  burn? 
After  the  crucible  is  cool,  re  weigh.    Compare  the  weight  of 
the  product  with  that  of  the  unburned  iron  (?).    The  experi- 
ment may  be  repeated,  using  tin. 

b.  The  burning  of  phosphorus.    (PRECAUTION.    Phosphorus 
must  be  kept  and  handled  only  under  water;  otherwise  it  may 
ignite,  and  serious  results  follow.}     Cover  the  bottom  of  a 
pneumatic  trough  with  water  to  a  depth  of  2  or  3  cm.    On 
the  water  float  a  porcelain  crucible  containing  a  piece  of 
phosphorus  the  size  of  a  small  pea. 

9 


Ignite  the  phosphorus  by  touching  it  with  a  hot  wire  or 
the  end  of  a  hot  file,  and  quickly  invert  over  the  crucible 
a  large  beaker  (or  a  wide- 
mouthed  bottle),  being  care- 
ful to  keep  the  rim  of  the 
beaker  below  the  surface 
of  the  water.  The  white 
powder  formed  by  the  burn- 
ing phosphorus  floats  in  the 
air  in  the  beaker  but  is 
gradually  dissolved  by  the 
water. 

Leave  the  beaker  in  posi- 
tion until  the  powder  has 
entirely  disappeared.  Note 
that  the  water  has  risen  in 
the  beaker.  How  do  you 
account  for  this  fact  ?  Is 
your  conclusion  in  accord 
with  the  results  obtained  by  burning  iron  in  air  ?  Suppose 
it  were  possible  for  you  to  collect  and  weigh  the  white 
powder  formed  by  the  burning  phosphorus,  how  would  you 
expect  its  weight  to  compare  with  that  of  the  unburned 
phosphorus  ? 

c.  The  burning  of  a  candle.  Hold  a  cold, 
dry,  wide-mouthed  bottle  over  a  candle  flame, 
.as  shown  in  Fig.  17.  Note  the  film  of  mois- 
ture collecting  on  the  bottle.  After  one  or  two 
minutes  remove  the  bottle  quickly  and  pour 
into  it  5  cc.  of  clear  limewater.  Place  the  palm 
of  the  hand  tightly  over  the  mouth  of  the  bottle 
and  shake  the  contents.  Note  any  change  in 
the  appearance  of  the  limewater. 

Clean  and  dry  the  bottle  and  repeat  the  experiment,  but 
omit    holding    the   bottle    over    the   candle    flame.     What 

10 


FIG.  16 


1=J, 


FIG. 17 


conclusions  do  you  draw  from  the  experiment  ?  How  do 
you  account  for  the  fact  that  a  burning  candle  gradually 
loses  weight,  while  iron  on  burning  increases  in  weight? 

EXERCISE  5 

CHEMICAL  ACTION  ;  ELEMENTS,  COMPOUNDS, 
MIXTURES 

Apparatus.  Burner ;  evaporating  dish  ;  ring  stand ;  magnet ;  mag- 
nifying glass ;  test  tubes. 

Materials.  Iron  wire,  10  cm.  in  length  ;  wooden  splint ;  2  or  3  g.  of 
sugar ;  1  g.  common  salt ;  piece  of  granulated  zinc  ;  sulf  uric  acid  ; 
2  g.  sulfur ;  2  g.  powdered  iron. 

a.  Chemical   action.    Hold  a  piece   of  iron   wire  in  the 
Bunsen  flame   for  a  few   seconds.     Is   the  iron   changed  ? 
Examine  it  when  it  has  cooled.   Have  the  properties  changed  ? 
Has  a  chemical  action  occurred  ? 

b.  Repeat  a,  using  a  splint  of  wood  in  place  of  the  iron 
wire.    How  does  the  change  produced  differ  from  that  in  a  >-. 
Has  a  chemical  action  occurred  ? 

c.  Place  enough  sugar  in  a  clean,  dry  test  tube  to  cover 
the  bottom  to  a  depth  of  1  cm.    Heat  it  gently  in  the  tip  of 
the  flame  as  long  as  any  changes  are  produced.    Note  all  the 
changes.    Is  the  product  sweet  ?    Is  it  soluble  in  water  ?   Do 
any  properties  remain  unchanged  ?    What  grounds  do  you 
have  for  assuming  that  a  chemical  action  has  taken  place  ? 

d.  Place  about  1  g.  of  common  salt  in  a  test  tube  and 
dissolve  it  in  a  little  water.    Pour  the  clear  solution  into  an 
evaporating-dish  and  evaporate  to  dryness  (Fig.  15).    What 
is  the  solid  left  ?    How  do  its  properties  correspond  to  those 
of  the  original  salt  ? 

e.  Cover  a  small  piece  of  zinc  in  a  test  tube  with  about 
5  cc.  of  water  and  add  carefully  3  or  4  drops  of  sulfuric 
acid.    Notice  that  the  zinc  dissolves  with  the  evolution  of  a 
gas.    Hold  a  burning  splint  at  the  mouth  of  the  test  tube 

11 


and  note  the  result.  After  the  action  has  entirely  ceased,  filter 
off  any  undissolved  zinc  and  evaporate  the  solution  to  dryness 
(hood)  as  in  d.  How  does  the  change  differ  from  that  in  d  ? 

/.  Elements;  compounds;  mixtures.  What  is  an  element? 
Are  iron  and  sulfur  included  in  the  list  of  elements  ?  Weigh 
out  separately  (on  paper)  2  g.  of  sulfur  and  2  g.  of  powdered 
iron  and  make  a  careful  list  of  their  properties.  Try  the 
effect  of  a  magnet  on  each.  Now  mix  the  two,  and  grind 
them  together  intimately  in  a  mortar.  Examine  the  product 
with  a  magnifying  glass.  Can  you  distinguish  the  iron  from 
the  sulfur  ?  Can  you  separate  them  with  a  magnet  ?  Have 
they  undergone  any  change  in  properties  ?  What  is  such  a 
material  called  ? 

Now  place  the  product  in  a  clean  test  tube  and  heat 
gently.  As  so^n  as  the  mass  begins,  to  glow,  quickly  with- 
draw the  tube  from  the  flame.  Does  the  mass  continue  to 
glow  ?  Now  heat  it  strongly  for  one  or  two  minutes ;  then 
cool  the  tube,  remove  the  substance  (it  may  be  necessary  to 
break  the  tube  to  do  so),  and  examine  the  product  with  a 
magnifying  glass.  Can  you  now  distinguish  between  the  iron 
and  the  sulfur  ?  Try  the  effect  of  the  magnet.  Of  what  is 
the  substance  composed  ?  When  elements  combine  chemi- 
cally, do  they  retain  their  original  properties  ?  What  is  the 
product  of  such  a  combination  called  ? 

EXERCISE  6 

COLLECTION   OF   GASES;     PREPARATION   OF   OXYGEN 
FROM  (.4)  MERCURIC  OXIDE,  (£)  SODIUM  PEROXIDE 

Apparatus.  250-cc.  wide-mouthed  bottles ;  glass  plate  ;  pneumatic 
trough  or  granite-ware  pan;  hard-glass  test  tube;  *  apparatus  Fig.  19. 

Materials.  0.5  g.  mercuric  oxide ;  wooden  splint  * ;  5  g.  sodium 
peroxide. 

a.  1.  Collection  of  gases.  Fill  a  wide-mouthed  bottle 
(250-cc.)  with  water.  Cover  its  mouth  with  a  glass  plate, 

12 


being  careful  to  exclude  all  air  bubbles.  Hold  the  plate 
firmly  in  place,  invert  the  bottle,  and  dip  its  mouth  into 
the  water  in  a  pneumatic  trough.  Remove  the  glass  plate. 
Why  does  the  water  remain  in  the  bottle  ?  Now  fill  the 
bottle  with  exhaled  air  by  placing  one  end  of  a  piece  of 
glass  or  rubber  tubing  under  the  mouth  of  the  bottle  and 
blowing  gently  through  the  other  end.  Before  the  bottle, 
so  filled,  is  removed  from  the  trough,  cover  its  mouth 
tightly  with  a  glass  plate.  The  bottle  so  covered  may  then 
be  placed  on  the  desk  in  either  an  upright  or  an  inverted 
position.  (When  should  it  be  placed  in  an  inverted  position  ?) 

2.  Fill  a  bottle  with  exhaled 
air  and  then  transfer  the  air  to 
another  bottle.  Draw  a  diagram 
to  show  the  method  of  doing  this.  FlG  18 

b.  Preparation  of  oxygen  from 

mercuric  oxide.  In  the  bottom  of  a  clean,  dry  test  tube 
place  about  1  g.  of  mercuric  oxide.  This  is  done  by  plac- 
ing the  oxide  near  the  end  of  a  narrow  strip  of  folded 
paper  and  introducing  it  carefully  into  the  tube,  as  shown 
in  Fig.  18.  On  inclining  the  tube  and  gently  tapping  the 
paper  the  oxide  will  be  deposited  in  the  bottom  of  the 
tube.  The  paper  is  now  withdrawn,  leaving  the  sides  of 
the  tube  perfectly  clean.  Now  hold  the  tube  between  the 
thumb  and  fingers  (Fig.  9),  and  apply  a  gentle  heat  to  the 
oxide.  The  tube  must  be  rotated  constantly,  to  distribute 
the  heat;  otherwise  it  may  be  melted.  During  the  heating 
insert  a  glowing  splint  from  time  to  time  into  the  mouth 
of  the  tube.  Note  the  result.  Continue  to  heat  as  long  as 
any  gas  is  evolved.  What  remains  in  the  tube  ?  How  has 
the  heat  affected  the  mercuric  oxide  ?  What  kind  of  change 
has  the  mercuric  oxide  undergone  (p.  14  of  text)  ? 

*c.  Preparation  of  oxygen  from  sodium  peroxide.  Sodium 
peroxide  is  a  white  solid  containing  41  per  cent  of  oxygen, 
and  when  treated  with  water,  a  part  of  this  is  set  free. 

13 


Arrange  an  apparatus  according  to  Fig.  19.  By  means  of  a 
short  piece  of  rubber  tubing  A  connect  the  funnel  B  with 
a  glass  tube  C,  pinching  the  rubber  tube  shut  with  a  screw 
clamp.  Place  about 
5  g.  of  sodium  per- 
oxide in  the  bottom 
of  D  and  partly 
fill  the  funnel  with 
warm  water.  Very 
cautiously  open  the 
screw  clamp  so  that 
the  water  will  run 
down  and  fall,  drop 
by  drop,  upon  the 
peroxide.  (The  fun- 
nel must  be  kept 
partially  filled  with 
water  (?)).  A  steady 
current  of  oxygen 

is  given  off.  Collect  a  bottle  of  the  gas  and  test  it  by  thrust- 
ing a  glowing  splint  into  the  bottle.  What  is  the  source  of 
the  oxygen  ?  What  substances  remain  in  the  generator  bottle 
(p.  27  of  text)  ? 

EXERCISE  7 

USUAL  LABORATORY  PREPARATION  OF  OXYGEN; 
PROPERTIES  OF  OXYGEN 

Apparatus.  Test  tubes;  test  tube  prepared  in  Exercise  2  (Fig.  2), 
connected  with  rubber  tube  as  shown  in  Fig.  20 ;  trough  and  wide- 
mouthed  bottles  shown  in  Fig.  20  ;  burner ;  deflagrating-spoon  ; 
4  pieces  of  window  glass  10  cm.  square ;  funnel ;  evapora ting-dish. 

Materials.  10  g.  potassium  chlorate ;  4  g.  manganese  dioxide ; 
wooden  splint ;  1  g.  of  sulfur ;  picture-frame  wire  20  cm.  long ;  bit 
of  cotton ;  filter  paper. 

a.  Preparation  of  oxygen  from  potassium  chlorate  (prelimi- 
nary experiment).  Select  two  test  tubes  of  the  same  size,  and 

14 


FIG.  19 


clean  and  dry  them  thoroughly.  Into  the  one  introduce  2  g.  of 
potassium  chlorate ;  into  the  other  introduce  2  g.  of  potassium 
chlorate  mixed  intimately  with  1  g.  of  manganese  dioxide. 

Now  heat  the  contents  of  the  two  tubes,  applying  the 
flame  so  that  both  tubes  are  equally  heated.  Eepeatedly 
thrust  a  glowing  splint  into  each  tube  in  order  to  detect 
any  oxygen  that  may  be  evolved.  Note  the  results.  What 
effect  has  the  manganese  dioxide  ?  Does  the  addition  of  the 
manganese  dioxide  enable  bne  to  obtain  an  increased  amount 
of  oxygen  (p.  26  of  text)  ?  What  term  is  applied  to  sub- 
stances which  act  like  the  manganese  dioxide  ? 

b.  Preparation  of  oxygen ;  usual  laboratory  method.  Mix 
intimately  on  paper  6  g.  of  potassium  chlorate  and  3  g.  of 
manganese  dioxide.  The  presence  of  impurities  in  the  mate- 
rials may  lead  to  a  serious  explosion  when  heat  is  applied ; 
hence  test  a  small  portion  of  the  mixture,  say  0.5  g.,  by 
heating  it  in  a  test  tube.  In  the  absence  of  impurities  the 
oxygen  is  evolved  quietly,  unaccompanied  by  .any  very 
marked  sparking  in  the  materials. 

Place  the  apparatus  prepared  in  Exercise  2  (Fig.  2)  on  a 
ring  stand  as  shown  in  Fig.  20,  and  connect  with  it  a  piece 
of  rubber  tubing  (7;  also  fill  4  wide-mouthed  bottles  (250-cc.) 
with  water  and  invert  them  in  a  pneumatic  trough,  as  shown 
in  the  figure.  Now  transfer  the  mixture  of  potassium  chlo- 
rate and  manganese  dioxide  to  the  glass  tube  A,  and  insert 
the  cork  (Fig.  20) ;  then,  holding  the  burner  in  the  hand, 
heat  the  mixture  gently  with  a  small  flame,  applying  the 
heat  at  first  to  the  upper  part  of  the  mixture.  The  flame 
must  not  strike  the  upper  part  of  the  test  tube,  as  the  cork 
may  be  ignited.  At  first  the  heat  expands  the  air  and  a 
few  bubbles  of  air  escape ;  then  the  oxygen  is  evolved. 
Regulate  the  heat  so  as  to  secure  a  uniform  and  not  too 
rapid  evolution  of  the  gas.  Will  the  gas  which  passes  over 
at  first  be  the  pure  oxygen  ?  Collect  four  250-cc.  wide- 
mouthed  bottles  of  the  gas.  Before  the  heat  is  withdrawn, 

15 


remove  the  cork  from  the  tube  (?).  What  is  the  source  of 
the  oxygen  ?  Place  the  tube  and  contents  aside  for  use  as 
described  in  d. 

c.  Properties  of  oxygen.  1.  Note  the  physical  properties 
(color,  odor,  taste,  solubility  in  water)  of  the  gas.  (The 
slight  cloud  that  is  often  present  when  oxygen  is  prepared 
from  potassium  chlorate  is  due  to  an  impurity  and  will  dis- 
appear if  the  gas  is  allowed  to  stand  over  water.) 


FIG.  20 

2.  Kepeatedly  thrust  a  glowing  splint  into  a  bottle  of 
the  gas. 

3.  Heat    some    sulfur    in    a    deflagrating-spoon   until    it 
begins   to   burn.     Note   the    color   and    size    of   the  sulfur 
flame.     Now   lower   the   burning    sulfur   into   a    bottle   of 
oxygen  and  note  the  change. 

4.  Tip  the  piece  of  picture-frame  wire  with  sulfur  by 
wrapping  a  very  small  bit  of  cotton  about  the  end  of  the 
wire  and  dipping  this  into  melted  sulfur  (for  this  purpose 
melt    a  little   sulfur  in    a    deflagrating-spoon).     Ignite  the 
sulfur   by   holding  it  in  a   Bunsen   flame    for    an  instant, 
and  then  thrust  the  wire  into  a  bottle  of  oxygen. 

16 


Describe  the  results  obtained  in  2,  3,  and  4.  What 
becomes  of  the  oxygen  ? 

d.  Separation  of  the  compounds  present  in  the  residue 
left  in  the  preparation  of  oxygen.  Heat  the  tube  containing 
the  residue  until  no  more  oxygen  is  evolved.  After  the 
tube  is  cool,  nearly  fill  it  with  water  and  shake  the  con- 
tents thoroughly.  After  a  few  minutes,  filter  off  the  solid 
matter  (what  is  it?),  repeating  the  filtration,  if  necessary, 
in  order  to  obtain  a  perfectly  clear  filtrate.  Evaporate 
about  one  third  of  the  liquid,  and  set  it  aside  until  crystals 
are  deposited.  Convince  yourself  that  the  substance  is  dif- 
ferent from  the  potassium  chlorate  with  which  you  started. 
What  is  the  compound  (p.  26  of  text)  ? 

EXERCISE  8 
THE  PREPARATION  AND  PROPERTIES  OF  HYDROGEN 

Apparatus.  Test  tube  ;  apparatus,  bottles,  and  trough  as  shown  in 
Fig.  21  (the  bottles  are  250-cc.,  wide-mouthed)  ;  beaker ;  stirring- 
rod  ;  60-cc.  bottle  ;  burner ;  evaporating-dish  ;  *  funnel. 

Materials.  Bit  of  sodium  (size  of  a  small  pea)  ;  filter  paper ; 
wooden  splints ;  10  g.  granulated  zinc ;  copper  sulf  ate  solution 
(R.  S.)  ;  sulfuric  acid. 

a.  Preparation  from  water.  Fill  a  test  tube  with  water 
and  invert  it  in  a  beaker  of  water.  Wrap  a  piece  of  sodium 
in  a  bit  of  filter  paper  previously  moistened  with  coal  oil. 
Raise  the  inverted  test  tube  until  its  mouth  dips  just  below 
the  surface  of  the  water  in  the  beaker,  and  quickly  insert 
the  sodium.  Stand  at  arm's  length,  as  a  slight  explosion 
sometimes  occurs.  Notice  that  the  sodium  decomposes  the 
water,  liberating  a  gas  which  is  caught  in  the  tube.  Place 
your  thumb  tightly  over  the  mouth  of  the  tube  to  prevent 
the  gas  from  escaping,  and  bring  the  tube  to  an  upright 
position.  Light  a  splint,  remove  the  thumb  from  the  tube, 
and  quickly  bring  the  flame  to  the  mouth  of  the  tube.  Does 

17 


the  gas  act  like  oxygen  ?  What  is  the  source  of  the  gas  ? 
What  other  methods  may  be  employed  for  obtaining  it  from 
the  same  source  ? 

b.  Preparation  from  acids  (usual  laboratory  method).  Pre- 
pare a  hydrogen  generator  according  to  Fig.  21.  D  represents 
a  wide-mouthed  bottle  of  about  250-cc.  capacity.  The  gas- 
delivery  tube  B,  C  is  the  same  as  that  used  in  the  prepara- 
tion of  oxygen  (Fig.  20).  A  rubber  stopper  for  the  bottle 


FIG.  21 

D  is  preferable,  although  a  good  cork  stopper  will  do.  The 
funnel  tube  A  must  extend  nearly  to  the  bottom  of  the 
bottle  (?).  Put  10  g.  of  granulated  zinc  (why  granulated?) 
into  D.  Pure  sulfuric  acid  will  not  react  with  pure  zinc ; 
hence  it  is  advisable  to  add  to  the  zinc  8  or  10  drops  of  a 
solution  of  copper  sulfate,  which  will  start  the  reaction. 
Now  pour  just  enough  water  through  the  funnel  tube  to 
cover  the  zinc. 

Prove  that  the  apparatus  is  air-tight  by  blowing  into  the 
delivery  tube  C  until  the  water  is  forced  nearly  to  the  top 
of  the  funnel  tube  ;  then  quickly  close  the  rubber  tube  either 
by  tightly  pinching  it  or  by  placing  the  tongue  firmly  against 
its  end.  If  the  apparatus  is  air-tight,  the  water  in  the  funnel 
tube  will  not  fall. 

18 


Prepare  some  dilute  sulfuric  acid  by  pouring  slowly,  a  few 
drops  at  a  time,  15  cc.  of  concentrated  acid  into  a  beaker 
containing  50  cc.  of  water.  Stir  the  water  with  a  glass  rod 
while  the  acid  is  being  added.  Notice  that  the  acid  is  poured 
into  the  water  —  never  the  reverse  (/). 

Cool  the  mixture  and  pour  a  few  drops  of  it  through  the 
funnel  tube.  Hydrogen  is  at  once  evolved.  Enough  of  the 
acid  must  be  added  from  time  to  time  to  cause  a  gentle  and 
continuous  evolution  of  the  gas.  An  excess  of  the  acid 
should  be  avoided,  however,  or  the  action  will  become  too 
violent  and  a  large  quantity  of  zinc  will  have  to  be  added 
at  the  close  of  the  exercise. 

It  is  evident  that  the  gas  which  passes  over  first  is  a  mix- 
ture of  hydrogen  and  air.  The  student  must  remember  that 
such  a  confined  mixture  of  hydrogen  and  air  explodes  with 
great  violence  if  ignited.  Hence  see  that  the  end  of  the  deliv- 
ery tube  is  not  brought  near  any  flame.  Determine  when 
the  hydrogen  is  free  from  air  by  repeatedly  collecting  a  test 
tube  full  of  gas  and  igniting  it,  holding  the  tube  mouth 
downward  (?).  If  pure,  the  gas  burns  quietly ;  otherwise 
there  is  a  slight  explosion.  After  all  the  air  has  been  ex- 
pelled from  the  generator,  collect  four  bottles  (250-cc.,  wide- 
mouthed)  of  the  gas. 

What  is  the  source  of  the  hydrogen  ?  What  is  the  use  of 
the  zinc  ? 

Remove  the  cork  from  the  generator,  add  a  few  more 
pieces  of  zinc,  and  set  aside.  Sufficient  zinc  should  be  used 
so  that  at  least  a  small  portion  of  it  remains  undissolved. 

c.  Properties  of  hydrogen.  1.  Thrust  a  lighted  splint  into 
a  bottle  of  the  gas  held  mouth  downward.  Slowly  withdraw 
the  splint  and  again  thrust  it  into  the  gas.  Describe  the 
results.  What  do  they  prove  ? 

2.  Fill  a  small  (60-cc.)  wide-mouthed  bottle  or  test  tube 
one-third  full  of  water  and  invert  it  in  a  pneumatic  trough. 
Displace  the  remaining  water  with  hydrogen  from  one  of  the 

19 


bottles.  What  does  the  bottle  now  contain  ?  Withdraw  it 
from  the  water  and,  holding  it  at  arm's  length,  quickly  bring 
it,  mouth  downward,  over  a  flame.  What  do  the  results 
prove  ? 

3.  Uncover  a  bottle  (mouth  upward)  of  the  gas.  After  a 
minute,  test  for  the  presence  of  hydrogen  with  a  lighted 
splint.  Eepeat,  holding  the  bottle  mouth  downward.  Describe 
the  results.  Is  the  gas  heavier  or  lighter  than  air  ? 

*4.  Without  removing  the  fragments  of  undissolved  zinc, 
pour  the  liquid  set  aside  in  Experiment  b  into  an  evapora ting- 
dish  and  boil  gently  on  a  ring-stand  support.  As  soon  as 
white  crusts  begin  to  form  on  the  side  of  the  dish,  just  above 
the  liquid,  filter  the  hot  liquid  into  a  beaker  and  set  it  aside 
to  cool.  How  does  the  product  which  separates  from  the 
filtrate  compare  in  properties  with  the  original  zinc  ?  What 
is  the  product  (p.  41  of  text)?  How  does  it  differ  in  com- 
position from  sulfuric  acid  ? 

EXERCISE  9 

THE  COMBUSTION  OF  HYDROGEN;  THE  OXY- 
HYDROGEN  BLOWPIPE 

Apparatus.  Hydrogen  generator  A  (Fig.  22)  attached  by  rubber 
tubing  C  to  a  drying-tube  B.  This  tube  is  filled  with  granulated 
calcium  chloride,  held  in  place  by  loose  plugs  of  cotton  placed  at 
each  end  of  the  tube.  D  is  a  glass  tube  drawn  to  a  jet. 

Materials.  Granulated  calcium  chloride ;  cotton ;  8  g.  zinc ;  cop- 
per sulfate  solution  (R.  S.)  ;  dilute  sulfuric  acid  ;  picture-frame  wire 
10  cm.  long ;  bit  of  charcoal. 

a.  Charge  the  generator  A  (Fig.  22)  with  6  or  8  g.  of 
zinc,  add  the  solution  of  copper  sulfate,  cover  with  water, 
and  add  dilute  sulfuric  acid  as  in  &,  Exercise  8.  Slip  a  piece 
of  rubber  tubing  over  the  tube  Z>,  collect  samples  of  the 
gas  in  test  tubes  over  water,  and  test  with  a  flame  to  see 
whether  the  hydrogen  is  free  from  air.  After  all  the  air  has 

20 


o 


m 


FIG.  22 


been  expelled,  wrap  a  towel  carefully  about  the  generator  and 
cautiously  ignite  the  hydrogen.  The  flame  is  nearly  invisible 
and  is  very  hot.  Test 
the  heat  of  the  flame 
by  holding  in  it  differ- 
ent objects,  such  as  a 
splint,  a  piece  of  picture- 
frame  wire,  a  bit  of 
charcoal. 

Finally,  hold  over 
the  flame  a  cold,  dry 
beaker  or  bottle  and 
note  the  liquid  depos- 
ited on  the  sides  of  the 
vessel.  Explain. 

b.  Examine  the  structure  of  the  oxyhydrogen  blowpipe. 
Draw  a  diagram  representing  a  cross  section  of  it.  Compare 
it  with  the  blast-lamp  used  in  fhe.  laboratory.  Why  not  have 
a  short  inner  tube  ? 

.EXERCISE  10 
OXIDATION  AND  REDUCTION 

Apparatus.  Hydrogen  generator  and  tubes  as  shown  in  Fig  23 
(A  is  the  hydrogen  generator,  B  is  a  drying-tube  filled  with  calcium 
chloride,  C  is  a  straight  glass  tube,  and  D  is  a  hard-glass  test  tube)  ; 
burner ;  apparatus  used  in  preparing  oxygen  (Fig  20). 

Materials.-  2  g.  copper  oxide  ;  calcium  chloride  sufficient  to  fill  the 
drying-tube  B ;  8  g.  zinc  ;  dilute  sulfuric  acid  for  preparing  hydrogen 
(see  Exercise  8  )  ;  4  g.  potassium  chlorate  ;  2  g.  manganese  dioxide. 

a.  Remove  the  tube  D  (Fig.  23),  introduce  into  it  1  or 
2  g.  Of  "copper  oxide,  and  return  it  to  the  position  shown  in 
the  figure. 

Now  generate  hydrogen  in  A  as  in  Exercise  8.  After  all 
the  air  has  been  expelled  from  the  apparatus  and  the  gen- 
erator wrapped  in  a  towel  (see  Exercise  9),  cautiously  heat 

21 


the  copper  oxide  to  redness,  being  careful  to  keep  the  flame 
away  from  the  mouth  of  the  tube  D  (?).  Note  the  conden- 
sation of  moisture  in  the  cold  portions  of  the  tube.  Is  there 
any  invisible  evidence  of  change  in  the  copper  oxide  ?  Explain. 
What  is  the  object  of  the  calcium  chloride  in  tube  B  ? 

b.  Disconnect  the  bottle  A  at  E  from  the  rest  of  the  ap- 
paratus and  force  a  little  air  through  the  tube  B  to  remove 


FIG. 23 

the  hydrogen  present.  Now  connect  the  apparatus  used  in 
preparation  of  oxygen  (Fig.  20)  at  E  to  the  tubes  B,  C,  and 
D.  Generate  oxygen  and  conduct  a  slow  current  of  the  gas 
through  B,  (7,  and  Z>,  at  the  same  time  heating  the  residue 
in  D  (?). 

c.  Explain   the  terms  reduction  and  oxidation  and  give 
an  example  of  each  process  from  the  above  experiment. 


22 


EXERCISE  11 

MEASUREMENT  OF  GAS  VOLUMES 
Apparatus.    Graduated  tube  and  cylinder  as  shown  in  Fig.  24. 

a.  (It  is  suggested  that  the  instructor  arrange  one  or 
more  pieces  of  apparatus  as  shown  in  Fig.  24.  The  students 
will  then  take  the  readings  and  solve 
the  problems.) 

Partially  fill  a  graduated  tube  with 
water  and  invert  it  in  a  cylinder  (or 
other  vessel)  of  water  as  shown  in 
Fig.  24.  Adjust  the  tube  until  the  level 
of  the  liquid  inside  and  outside  of  the 
tube  is  the  same;  then  take  the  read- 
ing of  the  volume  of  the  air  in  the 
tube.  Note  the  temperature  of  the  air 
(place  a  thermometer  by  the  side  of  the 
tube)  and  likewise  the  pressure  of  the  at- 
mosphere as  indicated  by  the  barometer. 
Insert  these  values  in  their  appropriate 
places  in  the  following  table: 


oo 


FIG.  24 


cc. 

o 


Volume  of  air  in  tube  ....-..-,. 

Temperature  of  air 

Vapor   pressure    at   temperature    of   air    (see 

Appendix)  .     .     .     .     ..,„.- mm. 

Barometric  pressure     .........       mm. 

Effective  pressure  on  gas  in  tube  (barometric 

pressure  less  vapor  pressure) mm. 

From  the  above  values  calculate  what  volume  the   air 
inclosed  in  the  tube  would  have  under  standard  conditions. 


23 


EXERCISE  12 


THE  DETERMINATION  OF  THE  WEIGHT  OF  ONE 
LITER  OF  OXYGEN;  ALSO,  OF  THE  PERCENTAGE  OF 
OXYGEN  IN  POTASSIUM  CHLORATE  (QUANTITATIVE) 

Apparatus.    Apparatus  shown  in  Fig.  25  ;  burner ;  500-cc.  beaker. 
Materials.    1  g.  potassium  chlorate. 

Prepare  the  form  of  apparatus  shown  in  Fig.  25.  A  repre- 
sents the  hard-glass  test  tube  used  in  the  preparation  of 
oxygen,  B  is  a  common  (narrow-mouthed)  bottle  having  a 
capacity  of  about  1  liter ;  rubber 
stoppers  should  be  used  in  both 
A  and  B.  The  rubber  tube  C 
is  provided  with  a  screw  clamp 
D,  for  closing  the  tube,  and  has 
in  its  end  a  glass  tube  E.  The 
end  of  this  glass  tube  is  drawn 
out  to  a  jet,  the  internal  diame- 
ter of  the  jet  being  about  2  mm. 
F  is  a  500-cc.  beaker. 

The   bottle   is   nearly    filled 

with  water,  as  shown  in  the  figure,  and  allowed  to  stand 
until  it  acquires  the  room  temperature.  The  tube  A  is  now 
removed  and  a  gentle  suction  is  applied  to  the  glass  jet  E. 
The  water  siphons  over,  through  the  tube  (7,  into  the  beaker 
and  is  allowed  to  run  for  a  moment  so  as  to  fill  completely 
both  the  rubber  and  the  glass  tubes  (C  and  E).  The  rubber 
tube  is  then  quickly  closed  with  the  screw  clamp  D. 

Now  thoroughly  clean  and  dry  the  tube  A  and  carefully 
weigh  it ;  then  introduce  about  1  g.  of  potassium  chlorate 
into  the  bottom  of  the  tube  by  means  of  a  folded  paper 
(Fig.  18),  and  reweigh.  Attach  the  tube,  as  shown  in 
Fig.  25,  care  being  taken  to  have  the  apparatus  uir-tiyht. 

24 


FIG. 25 


The  pressure  of  the  air  within  the  bottle  is  now  adjusted 
to  that  of  the  air  outside  as  follows :  Water  is  added  to  the 
beaker  F,  if  necessary,  until  the  end  of  the  glass  tube  E  is 
covered.  The  screw  clamp  is  then  opened  and  the  beaker  at 
once  raised  vertically  until  the  water  in  the  beaker  is  at  the 
same  level  as  the  water  in  the  bottle  and  is  retained  in  this 
position  until  the  screw  clamp  D  is  closed.  The  beaker  is 
then  emptied  and  returned  to  the  position  shown  in  Fig.  25. 

Now  open  the  clamp  D  and  gently  heat  the  potassium 
chlorate  in  A.  The  oxygen  is  evolved  and  forces  the  water 
from  the  bottle  into  the  beaker.  Gradually  increase  the  heat, 
and  continue  the  heating  until  all  the  oxygen  has  been  expelled 
(shown  by  the  fact  that  no  more  water  passes  over  into  F). 
Let  the  apparatus  stand  until  it  has  acquired  the  room  tem- 
perature, care  being  taken  that  the  glass  jet  E  is  kept  below 
the  surface  of  the  water  in  the  beaker  (?). 

Now  bring  the  level  of  the  water  in  the  beaker  to  that  of 
the  water  left  in  the  bottle,  and  while  holding  it  in  this 
position  close  the  screw  clamp  (?).  Carefully  measure  the 
water  in  the  beaker ;  also  take  the  reading  of  the  thermome- 
ter and  the  barometer.  Disconnect  the  tube  A  and  carefully 
reweigh.  Insert  the  values  in  the  following  table : 

Weight  of  tube  A g. 

Weight  of  tube  A  +  potassium  chlorate g. 

Weight  of  tube  A  +  potassium  chloride g. 

Weight  of  oxygen  evolved  (loss  in  weight  of  contents 

of  tube  A  on  heating)     ....... g. 

Volume  of  water  in  beaker.  =  volume  of  oxygen  evolved  _.  cc. 

Temperature  of  water ° 

Barometric  reading   .  mm. 

Value  of  vapor  pressure  (see  Appendix) mm. 

From  your  results  calculate  the  weight  of  1  liter  of  oxygen 
under  standard  conditions ;  also  calculate  the  percentage  of 
oxygen  in  potassium  chlorate.  Compare  your  results  with 
the  actual  values  (pp.  25  and  29  of  text). 

25 


EXERCISE  13 


A  STUDY  OF  THE  PROCESS  OF  DISTILLATION 

Apparatus.  Flask  (250-cc.)  ;  condenser  and  connections  as  shown 
in  Fig.  26,  or  apparatus  shown  in  Fig.  27 ;  ring  stands ;  wire  gauze 
12  cm.  square;  watch  glass. 

Materials.    10  cc.  alcohol. 

a.  (Two  or  more  students  may  work  together  if  the  appa- 
ratus is  not  available  for  each.)  Connect  a  liebig  condenser 
B  with  a  250-cc.  flask  J,  as  represented  in  Fig.  26.  The 
flask  is  set  on  a 
piece  of  wire  gauze 
supported  by  the 
iron  ring  attached 
to  the  ring  stand. 
The  tube  C  is  con- 
nected with  the 
water  pipe  by 
means  of  rubber 
tubing,  and  a  cur- 
rent of  cold  water  is 
conducted  through 
the  outer  tube  of  the  condenser,  escaping  through  the  tube  D. 
(Why  is  cold  water  forced  in  at  C  rather  than  at  7>?) 

Fill  the  flask  one-fourth  full  of  hydrant  or  well  water  and 
boil  until  50  cc.  or  more  of  liquid  has  collected  in  the 
receiver  E.  (In  case  condensers  are  not  available,  the  appa- 
ratus shown  in  Fig.  27  may  be  used.  When  this  is  used 
the  steam  from  the  boiling  water  in  flask  A  is  condensed 
by  conducting  it  through  B  into  the  test  tube  C,  which  is 
kept  cold  by  the  ice  water  in  the  beaker  D.) 

Compare  the  distillate  (distilled  water)  with  the  hydrant 
water  in  appearance  and  in  taste  (?). 

26 


Fm.  26 


Place  4  or  5  drops  of  the  distilled  water  on  a  watch  glass 
and  evaporate,  holding  the  watch  glass  10  or  15  cm.  above 
the  tip  of  the  flame.  Is  there  any  residue  ?  Repeat,  using 
hydrant  water.  Why  is 
distilled  water  used  in  the 
laboratory  ? 

b.  Eepeat  the  distilla- 
tion, using  a  sample  of 
muddy  water  in  A  (?). 

c.  Pour  1  or  2  cc.   of      ( 
alcohol  into-  a  porcelain 
dish  -and  bring  a  flame       < 
in    contact    with   it.     Is 
the  alcohol  inflammable  ? 
Now    distill    a    mixture 

of  10  cc.  of  alcohol  (boil- 


1) 


FIG.  2' 


ing  point  78.3°)  and  30  cc. 
of  water.  Collect  the  first 
1  or  2  cc.  of  the  distillate  in  an  evaporating  dish  and  test 
with  a  flame.  In  the  same  way  test  successive  portions  of 
the  distillate.  Does  there  seem  to  be  a  partial  separation  of 
the  two  liquids  ?  In  this  way  a  mixture  of  liquids  boiling 
at  different  temperatures  may  generally  be  separated  more  or 
less  perfectly.  The  process  is  termed  fractional  distillation. 


EXERCISE  14 
THE  COMPOSITION  OF  WATER 

Apparatus.  Hydrogen  generator  and  tubes  as  shown  in  Fig.  28 
and  described  below ;  balance ;  apparatus  shown  in  Fig.  25,  but 
without  test  tube  and  stopper. 

Materials.  10  g.  granulated  zinc  ;  2  g.  black  powdered  copper  oxide ; 
sulfuric  acid;  granular  calcium  chloride,  sufficient  to  fill  tubes  B  and  D. 

a.  Recall  the  experiments  included  under  Exercises  9 
and  10.  What  do  the  results  show  in  reference  to  the 

27 


composition  of  water  ?  Is  the  process  employed  in  Exercise  10 
one  of  synthesis  or  analysis  ?  Are  the  results  qualitative  or 
quantitative  in  character  ? 

*&.  The  experiments  included  under  Exercise  10,  may  be 
modified  in  the  following  way  so  as  to  give  quantitative 
results.  Arrange  an  apparatus  as  shown  in  Fig.  28,  in  which 
A  represents  the  hydrogen  generator,  and  B  and  I)  are 
tubes  filled  with  dry  calcium  chloride.  The  hard-glass  tube 

O 


E 


FIG.  28 


C  and  the  porcelain  boat  E  are  obtained  from  the  store- 
room. The  tube  is  about  35  cm.  in  length.  Introduce  about 
2  g.  of  black  oxide  of  copper  into  the  boat  and  weigh  accurately 
to  milligrams.  Introduce  the  boat  into  the  glass  tube  so 
that  the  end  of  the  boat  is  about  8  cm.  from  the  end  of 
the  tube  connected  with  D.  Close  the  ends  of  tube  D 
with  short  pieces  of  rubber  tubing,  one  end  of  each  being 
closed  with  a  small  glass  rod ;  then  weigh  the  tube  accu- 
rately. Eemove  the  rubber  tubes  and  glass  rods,  carefully 
preserving  them  for  use  when  the  tube  is  again  weighed. 
Now  connect  the  apparatus  as  shown  in  the  figure,  taking 
care  to  render  it  air-tight.  How  is  this  determined  ?  Gen- 
erate hydrogen  slowly,  and  when  the  apparatus  is  free  from 
air,  heat  the  boat  very  gently,  using  the  wing-top  burner. 
Gradually  increase  the  heat,  all  the  time  maintaining  the 
slow  current  of  hydrogen.  When  the  copper  oxide  is  reduced, 

28 


or  nearly  so,  withdraw  the  heat  but  maintain  the  current  of 
hydrogen  until  the  apparatus  is  cool.  If  any  of  the  water 
formed  remains  condensed  in  the  end  of  tube  C,  a  very 
gentle  heat  is  cautiously  applied  (the  flame  must  not  strike 
the  tube)  until  it  is  driven  into  the  tube  D. 

When  the  apparatus  has  acquired  the  room  temperature, 
disconnect  A  from  the  remainder  of  the  apparatus  and 
attach  D  (Fig.  28)  by  a  short  piece  of  rubber  tubing  to  the 
short  bent  glass  tube  in  bottle  B  of  Fig.  25.  The  bottle  is 
filled  with  water,  and  a  portion  of  it  is  slowly  siphoned 
over  through  C,  D  (Fig.  25).  In  this  way  a  current  of  air 
is  drawn  through  the  apparatus,  displacing  the  hydrogen. 
Finally,  disconnect  the  apparatus,  and  at  once  close  the  ends 
of  the  tube  D  (Fig.  28)  with  the  rubber  tubes  provided  with 
glass  rods.  Weigh  the  boat  and  contents;  also  the  tube  Z>. 
From  your  results  calculate  the  composition  of  water.  Com- 
pare your  results  with  those  obtained  by  other  members  of 
the  class.  Calculate  the  general  average  of  all  the  results. 
How  does  this  result  compare  with  the  actual  values  (p.  77  of 
text).  What  sources  of  error  are  included  in  the  experiment  ? 

EXERCISE  15 

THE  PREPARATION  AND  PROPERTIES  OF  HYDROGEN 
PEROXIDE 

Apparatus.  Test  tube;  200-cc.  beaker;  glass  rod;  funnel  and 
filter  paper. 

Materials.  10  cc.  of  ordinary  hydrogen  peroxide  solution ;  wooden 
splint ;  1  g.  manganese  dioxide  (powder) ;  starch  paste  (R.S.) ;  crystal 
potassium  iodide;  6  cc.  ether;  potassium  dichromate  (R.S.);  1  g. 
sodium  peroxide ;  ice  water  (100  cc.)  ;  piece  of  blue  litmus  paper ; 
sulfuric  acid. 

a.  What  is  the  strength  of  the  hydrogen  peroxide  solu- 
tions sold  by  the  druggist  (p.  83  of  text)?  Pour  3  cc.  of 
the  solution  into  a  large  test  tube  and  add  1  g.  of  finely 

29 


powdered  manganese  dioxide.  Test  the  gas  evolved  with  a 
glowing  splint  (?).  What  kind  of  an  agent  is  hydrogen 
peroxide  ? 

Filter  the  mixture  remaining  in  the  tube.  The  solid  is 
the  unchanged  manganese  dioxide.  In  what  other  experi- 
ment has  manganese  dioxide  been  used  to  assist  in  bringing 
about  a  chemical  action,  the  dioxide  apparently  at  least 
undergoing  no  change  ? 

b.  To  1  cc.  of  starch  paste,  add  4  cc.  of  water.    Dissolve 
in  this  a  small  crystal  of  potassium  iodide  and  then  add  a 
few  drops  of  a  solution  of  hydrogen  peroxide.    The  peroxide 
liberates  the  iodine  from  the  potassium  iodide  and  the  result- 
ing free  iodine  colors  the  starch  paste.    Note  the  results. 

c.  Pour  3  cc.  of  the  solution  of  hydrogen  peroxide  into  a 
test  tube  and  add  an  equal  volume  of  ether  (CAUTION  :  ether 
is   very  inflammable).     Shake  the  solution  vigorously  and 
notice  that  the1  ether  quickly  rises  to  the  top  of  the  tube 
when  the  tube  is  set  aside.    Now  add  1  drop  of  a  solution  of 
potassium  dichromate  and  again  shake  the  mixture.   Note  the 
color  of  the  layer  of  ether  now.    A  blue  color  in  the  ether 
constitutes  a  delicate  test  for  hydrogen  peroxide. 

d.  When  sodium  peroxide   is  added  to  water,  hydrogen 
peroxide  is  formed,  but   this  decomposes  even  at  ordinary 
temperatures  into  water  and  oxygen  (p.  27  of  text).    If  the 
temperature   is   kept   low   however,  the  hydrogen  peroxide 
remains  unchanged  and  it  is  possible  in  this  way  to  prepare 
the  compound.    To  prepare  the  peroxide  proceed  as  follows : 
Add  1  g.  of  sodium  peroxide,  a  little  at  a  time,  to  100  cc.  of 
ice  water.    Now  add  dilute  sulfuric  acid,  a  few  drops  at  a 
time,  to  the  liquid  (stir  thoroughly  with  a  glass  rod)  until 
a  drop  of  the   resulting   liquid  placed  on  a  piece  of  blue 
litmus  paper  changes  the  blue  to  a  red  color.    Then  test  the 
liquid  for  the  presence  of  hydrogen  peroxide  in  accordance 
with  the  methods  given  above  under  b  and  c. 


30 


EXERCISE  16 

STATES  OF  MATTER 

Apparatus.    Watch  crystal;    500-cc.  beaker;    thermometer  grad- 
uated to  at  least  110°;  ring  stand  and  burner. 

Materials.    1  cc.  ether  or  chloroform  ;  10  cc.  benzene ;  pieces  of  ice. 

a.  Place  about  1  cc.  of  ether  or  of  chloroform  on  a  watch 
crystal  and  blow  upon  the  surface  of  the  liquid.    Account 
for  the  rapid  evaporation.    Do  you  notice  any  change  in  the 
temperature  of  the  watch  glass  ?    Explain. 

b.  Pour  about  250  cc.  of  distilled  water  into  a  suitable 
flask  or  beaker,  and  place  a  thermometer  in  the  liquid  so 
that  the  temperature  may  be  noted.    Now  heat  the  water  at 
such  a  rate  that  the  temperature  rises  slowly  but  steadily. 
At  what  temperature  do  you  observe  the  formation  of  bubbles  ? 
Where  do  they  appear  to  form  ?   Of  what  are  they  composed  ? 
At  about  what  temperature  do  larger  bubbles  begin  to  form 
at  the  bottom  of  the  vessel  ?    What  becomes  of  them  ?    Ex- 
plain.   At  what  temperature  do  they  move  freely  up  through 
the  liquid  to  the  surface  ?    Do  they  get  larger  or  smaller  as 
they  rise  ?    Why  ?    When  the  water  is  gently  boiling,  try  in- 
creasing the  heat.  Is  the  boiling  any  more  energetic  ?  Does  the 
temperature  rise  any  ?  How  do  you  define  the  boiling  point  ? 

c.  Pour  about  10  cc.  of  benzene  into  a  clean,  dry  hard- 
glass  test  tube.    This  liquid  is  inflammable  and  must  be  kept 
away  from  all  flames. .  Pour  into  a  beaker  some  ice  water  in 
which   some   pieces  of  ice   are   floating.     Now  immerse  in 
this  ice  water  that  part  of  the  test  tube  which  is  filled  with 
benzene.    Stir  the  benzene  constantly  with  a  thermometer, 
noting  the  temperature  from  time  to  time.  Carefully  note  the 
temperature  when  the  benzene  begins  to  freeze  and  continue 
the  reading  until  the  entire  liquid,  or  nearly  all  of  it,  is  frozen. 
Now  remove  the  tube  from  the  ice  water  and  hold  the  lower 

31 


part  of  it  in  the  hand  until  the  benzene  is  melted,  noting  the 
temperature  during  this  change.  Note  the  results  and  discuss. 
d.  Experiment  c  may  be  repeated,  using  water  in  the  test 
tube  and  immersing  it  in  a  freezing-mixture  made  by  mixing 
3  parts  of  powdered  ice  with  1  part  of  common  salt. 


EXERCISE  17 

THE  FORMATION  OF  CHARCOAL  AND  COKE 

Apparatus.  Hard-glass  test  tube  A  connected  as  shown  in  Fig.  29  ; 
B  is  a  test  tube  fitted  with  a  glass  tube  C  drawn  to  a  jet;  large 
beaker  ;  porcelain  dish  ;  burner. 

Materials.  Small  pieces  of  hard  wood  (sawdust  will  do)  sufficient 
to  half  fill  the  hard-glass  test  tube  ;  pieces  of  soft  coal  sufficient  to 
half  fill  the  test  tube  ;  blue  and  red  litmus  paper. 

a.  Half  fill  the  tube  A  (Fig.  29)  with  hard-wood  splints 
or  sawdust  and  connect  it  as 

The 


shown  in  the  figure. 
tube  B  is  kept  cool  by  ice 
water  in  the  beaker.  Heat 
the  wood  in  A,  gradually  in- 
creasing the  heat  until  no 
further  change  takes  place. 
During  the  heating,  test  the 
gas  escaping  from  the  jet 
C  to  determine  whether  it 
will  burn  (?). 

When  the  tube  A  is 
cool,  remove  the  residue  (?). 
Note  its  properties.  Is  it 
combustible  ? 

Note  the  odor  and  appear- 
ance  of  the  liquid  condensed 

in  B.    Name  two  important  compounds  prepared  commer- 
cially from  the  liquid  obtained  by  heating  hard  wood  in  the 

32 


FIG<  29 


absence  of  air  (p.  121  of  text).    What  name  is  applied  to 
the  process  undergone  by  the  wood  ? 

b.  Repeat  experiment  a,  substituting  small  pieces  of  soft 
coal  for  the  wood.  Describe  the  results.  What  is  left  in  the 
tube  A  ?  The  liquid  condensed  in  B  is  known  as  eoal  tar 
(p.  306  of  text).  Note  its  appearance  and  odor. 

EXERCISE  18 
A  FURTHER  STUDY  OF  CARBON 

Apparatus.    Hard-glass  test  tube  ;  porcelain  dish ;  burner ;  funnel. 

Materials.  3  g.  sugar ;  test  tube  one-fourth  full  of  bone  black ;  1  cc. 
litmus  solution ;  filter  paper ;  common  acids ;  3  g.  copper  oxide  and 
an  equal  bulk  of  powdered  charcoal ;  5  cc.  limewater  (R.S.). 

a.  Heat  2  or  3.  g.  of  sugar  in  a  test  tube  until  no  further 
change  takes  place.    Note  the  results.    What  is  the  residue  ? 

b.  Bring  a  cold  porcelain  dish  into  a  small  luminous  Bun- 
sen  flame.    Note  the  deposit.    What  is  this  form  of  carbon 
called  ?    In  what  other  forms  does  carbon  exist  ? 

c.  Put  into  a  small  flask  enough  bone  black  to  fill  a  test 
tube  one-fourth  full  and  pour  over  it  about  50  cc.  of  water, 
to  which  has  been  added  a  few  drops  of  a  solution  of  litmus 
or  indigo.    Thoroughly  mix  the  contents  of  the  flask ;   then 
heat  gently  for  a  few  minutes,  and  filter.    If  the  filtrate  is 
not  decolorized,  repeat  the  process,  using  more  bone  black. 
What  is  the  composition  of  bone  black  ?  By  what  other  name 
is  it  known  ?    What  use  does  this  experiment  suggest  for  it  ? 

d.  Is  carbon  an  active  element  at  ordinary  temperatures  ? 
Test  it  with  the  common  acids.    How  does  the  charring  of 
wood  preserve  it  ? 

e.  Mix  together  in  a  mortar  2  or  3  g.  of  black  copper  oxide 
and  an  equal  bulk  of  powdered  charcoal.    Transfer  to  a  hard- 
glass  test  tube  and  heat  gently.    The  copper  oxide  is  reduced 
to  copper,  the  oxygen  combining  with  the  hot  carbon  to 
form  carbon  dioxide. 

33 


EXERCISE  19 


O 


A  STUDY  OF  CARBON  DIOXIDE 

Apparatus.  Hydrogen  generator  with  connections,  as  shown  in 
Fig.  30  ;  three  250-cc.  bottles ;  small  beaker  or  test  tube  ;  hard-glass 
test  tube. 

Materials.  5  pieces  of  marble  (size  of  walnuts) ;  hydrochloric  acid ; 
splints ;  limewater  (R.  S.) ;  3  g.  of  copper  oxide  and  an  equal  bulk 
of  powdered  charcoal. 

a.  Usual  laboratory  method  for  preparing  carbon  dioxide. 
Place  some  pieces  of  marble  in  your  hydrogen  generator  and 
connect  as  shown  in  Fig.  30.  Add  water  through  the  funnel 
tube  until  the  marble  is  cov- 
ered with  the  liquid;  then 
add  hydrochloric  acid,  a  few 
drops  at  a  time.  Collect  three 
bottles  of  the  gas  by  displace- 
ment of  air.  To  test  when 
filled,  hold  a  burning  splint 
at  the  mouth  of  the  bottle ; 
the  gas  will  extinguish  the 
flame.  Why  not  collect  the 
gas  over  water  as  in  the  case  • 
of  oxygen  and  hydrogen  ? 

&.  Thrust  a  burning  splint 
into  one  of  the  bottles  of  the  gas  (?).    The  results  suggest 
what  use  for  the  gas  ? 

c.  Devise  an  experiment  to  show  whether  the  gas  is  heavier 
or  lighter  than  air.     Attempt  to  pour  it  from  one  bottle  to 
another,  as  you  would  a  liquid,  and  test  with  a  burning  splint 
for  its  presence  in  the  second  bottle  (?). 

d.  Pass  a  few  bubbles  of  the  gas  through  10  cc.  of  lime- 
water  (?).     This  serves  as  a  good  test  for  carbon  dioxide. 

34 


M 


7T 


B 


FIG.  30 


e.  Prove  that  the  air  exhaled  from  the  lungs  contains 
carbon  dioxide ;  also  prove  that  it  is  formed  when  ordinary 
fuels  burn. 

*/.  Repeat  experiment  e,  Exercise  18,  and  prove  that 
carbon  dioxide  is  evolved. 

EXERCISE  20 

PREPARATION  AND  PROPERTIES  OF  NITROGEN 

0 

Apparatus.  250-cc.  flask,  with  cork  and  glass  delivery  tube,  like 
that  used  in  preparing  oxygen  (B,  C,  Fig.  20) ;  ring  stand ;  burner ; 
pneumatic  trough  ;  3  wide-mouthed  bottles. 

Materials,    3  g.  ammonium  chloride ;  6  g.  sodium  nitrite. 

a.  Recall  experiment  &,  Exercise  4.   What  is  the  gas  left 
in  the  beaker  after  the  combustion  of  the  phosphorus  ? 

b.  In  a  250-cc.  flask  introduce  a  mixture  of  3  g.  of  ammo- 
nium chloride  and  6  g.  of  sodium  nitrite,  and  add  20  cc.  of 
water.    Provide  the  flask  with  a  one-hole  cork  and  delivery 
tube  so  that  the  evolved  gas  may  be  collected  over  water, 
as  in  the  case  of  oxygen  and  hydrogen.   Have  at  hand  a  vessel 
of  cold  water  so  that  the  flask  may  be  cooled  by  lowering 
it  into  the  water  in  case  the  action  becomes  too  violent. 

Clamp  the  flask  and  apply  a  very  gentle  heat,  moving  the 
burner  about  with  the  hand.  As  soon  as  the  action  begins, 
withdraw  the  heat.  After  the  air  has  been  expelled  from 
the  apparatus,  fill  three  bottles  (250-cc.)  with  the  gas.  If  the 
action  becomes  too  violent,  immerse  the  flask  in  cold  water. 

Write  the  equations  for  the  reactions  involved  (p.  130 
of  text). 

Note  the  physical  properties  of  the  gas.  Can  it  be  poured 
from  one  bottle  to  another  as  in  the  case  of  carbon  dioxide  ? 

Is  the  gas  combustible  (test  with  burning  splint)  ?  Is  it  a 
supporter  of  combustion  ? 


35 


EXERCISE  21 
THE  COMPOSITION  OF  AIR 

Apparatus.    Test  tube;  beakej*;  apparatus  shown  in  Fig.  31. 

Materials.  10  cc.  ice  water ;  5  g.  potassium  hydroxide  dissolved  in 
5  cc.  water  and  cooled  to  room  temperature ;  4  g.  pyrogallic  acid  dis- 
solved in  10  cc.  water ;  bit  of  calcium  chloride ;  10  cc.  limewater 
(R.S.). 

a.  Experiments  already  performed  have  proved  the  pres- 
ence of  certain  constituents  of  the  air.    Enumerate  the  ex- 
periments and  their  bearing  on  the  composition  of  air. 

b.  Thoroughly  dry  the  outside  of  a  test  tube  or  beaker 
and  partially  fill  it  with  ice  water.  What  is  the  liquid  which 
condenses  on  the  outside  of  the  container  ?     What  is  the 
source  of  this  liquid  ?  Place  a  small  piece  of  calcium  chloride 
on  a  watch  glass  and  leave  it  exposed  to  the  air  for  two  or 
more  hours.     Note  the  results.     (A  substance  which,  like 
calcium  chloride,  takes  up  moisture  from  the  air  is  said  to 
be  deliquescent  (p.  411  of  text).) 

c.  Pour  5  cc.  of  limewater  into  a  small  beaker  and  expose 
it  to  the  air  for  one  half  hour.    What  do  the  results  indicate  ? 

*d.  Determination  of  the  relative  amounts  of  nitrogen  and 
oxygen  in  the  air  (quantitative).  The  relative  volumes  of 
oxygen  and  nitrogen  in  the  air  may  be  determined  by  bring- 
ing in  contact  with  a  definite  volume  of  air  a  liquid  which 
absorbs  the  oxygen  and  in  so  doing  flows  into  the  tube  which 
contains  the  air,  and  fills  a  space  equal  to  that  previously 
occupied  by  the  oxygen.  The  volume  of  this  liquid  can  be 
easily  measured  and  the  volume  of  the  absorbed  oxygen 
ascertained. 

The  solution  used  to  absorb  the  oxygen  soon  loses  its 
strength  on  exposure  to  air;  the  experiment  must  there- 
fore be  performed  rapidly.  Before  preparing  the  solution 

36 


the  student  should  practice  the  manipulations  involved  in 
the  experiment,  as  skill  is  required  for  accurate  results. 

Arrange  an  apparatus  like  that  shown  in  Fig.  31.  A  repre- 
sents a  test  tube  about  15  cm.  in  length  (use  the  hard-glass 
tube  employed  in  the  preparation  of  oxygen).  The  tube  is 
fitted  with  a  two-hole  rubber  stopper.  One  hole  is  closed 
with  a  glass  rod  B,  while  the  other 
is  fitted  with  a  small  glass  tube,  the 
upper  end  of  which  extends  4  or 
5  cm.  abov£  the  stopper.  A  piece  of 
soft-rubber  tubing  C,  12  or  15  cm.  in 
length,  connects  the  glass  tube  with  a 
small  funnel,  as  shown  in  the  figure. 

Close  the  rubber  tube  tightly  with 
the  screw  clamp  D.  Disconnect  the 
test  tube  and  remove  the  glass  rod  B 
from  the  stopper  preparatory  to  per- 
forming the  experiment. 

Add  the  solution  of  potassium  hy- 
droxide to  the  solution  of  pyrogallic' 
acid,  mix,  and  at  once  pour  the  result- 
ing liquid  into  the  funnel  E.  Quickly 

open  the  screw  clamp  D  until  the  rubber  tube  and  the 
glass  tube  are  both  filled  with  the  liquid,  and  then  close 
the  clamp  tightly. 

Connect  the  test  tube,  holding  it  by  the  rim  to  avoid  heat- 
ing the  contained  air,  and  insert  the  glass  rod  in  the  cork. 
The  air  inclosed  in  the  tube  is  now  at  the  same  temperature 
and  pressure  as  the  surrounding  air. 

Now  open  the  screw  clamp.  The  liquid  flows  in,  absorb- 
ing the  oxygen.  When  the  liquid  ceases  to  enter,  grasp  the 
tube  by  the  rim  and  invert  it,  as  shown  by  the  dotted  lines 
of  the  figure,  adjusting  it  so  that  the  level  of  the  liquid  is 
the  same  in  both  tube  and  funnel  (?) ;  then  clamp  the  rubber 
tube  tightly  and  return  the  test  tube  to  its  original  position. 

37 


FIG. 31 


Mark  the  volume  of  the  air  originally  inclosed  in  the  tube 
by  placing  a  narrow  strip  of  gummed  paper  about  the  tube 
at  the  lower  end  of  the  stopper ;  mark  also,  by  a  strip  of 
paper  placed  at  the  level  of  the  liquid  in  the  tube,  the  vol- 
ume of  the  oxygen  absorbed. 

Disconnect  the  tube  and  rinse  it.  Measure  the  volume  of 
the  tube  to  each  strip  of  paper  by  pouring  in  water  from  a 
graduated  cylinder.  From  these  measurements  calculate  the 
number  of  volumes  of  oxygen  and  nitrogen  in  100  volumes 
of  air. 

NOTE.  This  experiment  disregards  the  presence  in  the  air  of  all 
constituents  other  than  oxygen  and  nitrogen.  The  volume  of  such 
constituents,  however,  in  the  amount  of  air  taken  is  smaller  than  the 
unavoidable  errors  in  the  experiment. 

EXERCISE  22 

A  STUDY  OF  SOLUTIONS 

Apparatus.  Test  tubes ;  funnel  and  filter  paper ;  100-cc.  beaker ; 
watch  glass ;  ring  stand  and  burner ;  apparatus  shown  in  Fig.  32 
(A  is  a  250-cc.  flask,  B  is  a  thermometer,  and  C  an  open  glass  tube). 

Materials.  2  crystals  of  potassium  permanganate ;  0.2  g.  powdered 
calcium  sulf  ate ;  3  g.  common  salt ;  3  g.  potassium  nitrate ;  1  g.  sugar ; 
10  cc.  carbon  tetrachloride  (R.  S.) ;  1  cc.  oil  (cotton-seed  or  olive) ; 
10  g.  sodium  thiosulf  ate. 

a.  Nearly  fill  two  test  tubes  with  water  and  set  them  in 
a  rack.     Drop  into  each  a  small  crystal  of  potassium  per- 
manganate.   Shake  the  contents  of  one  tube  and  repeat  the 
shaking  after  a  few  minutes  but  do  not  move  the  other  tube. 
At  the  close  of  the  laboratory  period  note  the  appearance  of 
the  liquid  in  each  tube  (?). 

b.  Introduce  about  0.2  g.  of  finely  powdered  calcium  sul- 
fate  into  a  test  tube  and  add  5  cc.  of  distilled  water.    Shake 
the  mixture  thoroughly  and  set  it  aside  for  10  minutes.    Is 
there  any  evidence  that  the  solid  is  soluble  in  water  ?   Now 

38 


filter  a  few  drops  of  the  liquid  (?),  collecting  the  filtrate  on 
a  watch  glass.  Set  the  glass  on  a  small  beaker  half  full  of 
boiling  water  (Fig.  33)  until  the  liquid  is  evaporated  (?). 

c.  Place  exactly  3  g.  of  common  salt  in  one  test  tube  and 
an  equal  weight  of  potassium  nitrate  in  another.   Add  to  each 
exactly  1  cc.  of  water  and  heat  each  tube  until  the  water 
boils.    If  the  solid  does  not  dissolve,  add  an  additional  cubic 
centimeter  of  water  and  again  heat.  Repeat 

until  the  solid  in  each  tube  is  dissolved. 
Compare  the  solubilities  of  the  two  solids 
in  the  boiling  water. 

Cool  the  solutions  in  each  tube  and 
note  the  approximate  amounts  of  solids 
separating  (?)  (compare  the  results  with 
the  table  of  solubility  of  solids  given  on 
page  561  of  text). 

d.  Introduce  about  0.5  g.  of  sugar  into 
each  of  two  test  tubes.    To  the  one  tube 
add  5  cc.  of  water  and  to  the  other  5  cc. 
of  carbon  tetrachloride  (a  low-boiling  gaso- 
line may  be  used  in  place  of  the  carbon 
tetrachloride,  but  if  used,  great  care  must 
be  taken  to  avoid  any  flame,  as  the  gaso- 
line is  very  inflammable).    Shake  the  tubes  gently  and  note 
the  results.     Repeat  the  experiment,  substituting  a  small 
bit  of  lard  or  an  oil  for  the  sugar.    How  could  you  remove 
stains  on  cloth,  due  to  (1)  a  sugar  sirup  (molasses) ;   to  (2) 
oils  or  grease ;  to  (3)  a  mixture  of  the  two  ? 

e.  Introduce  into  a  test  tube  10  g.  of  sodium  thiosulfate 
(ordinary  "  hypo "  of  the  photographer)  and  add   2  cc.  of 
water.    Heat  the  tube  gently  until  a  uniform   solution  is 
obtained,  care  being  taken  that  no  particles  of  the  solid  remain 
on  the  side  of  the  tube ;   stopper  the  tube  loosely  with  a 
plug  of  cotton  and  set  it  aside  until  the  solution  is  cold.   If 
sufficient  care  ha,s  been  taken,  no  solid  will  have  separated. 

39 


FIG.  32 


Now  remove  the  cotton  plug  and  drop  into  the  solution  a 
bit  of  the  solid  "  hypo "  as  large  as  a  pin  point.  Note  the 
results  (hold  the  tube  in  a  good  light)  and  explain. 

/.  Prepare  an  apparatus  as  shown  in  Fig.  32.  A  is  a  small 
flask,  B  is  a  thermometer,  and  C  an  open  glass  tube.  Pour 
some  water^into  A  and  heat  it  to  boiling,  noting  the  tem- 
perature of  the  liquid  as  the  boiling  continues  (?).  Now 
withdraw  the  flame  and  add  common  salt  to  the  water  until 
it  is  saturated-  then  determine  the  boiling  point  of  the 
solution  (?). 

EXERCISE  23 

DETERMINATION  OF  THE  SOLUBILITY  OF 
COMMON  SALT  (QUANTITATIVE) 

Apparatus.  60-cc.  bottle ;  evaporating-dish  with  watch-glass 
cover ;  beaker,  tripod,  and  burner  as  shown  in  Fig.  33  ;  funnel  and 
filter  paper ;  thermometer. 

Materials.    15  g.  common  salt. 

a.  Introduce  15  g.  of  common  salt  into  a  60-cc.  bottle 
and  add  40  cc.  of  water.  Shake  <- —  , 

the  mixture  vigorously  and  set 
aside,  repeating  the  shaking  sev- 
eral times  at  intervals  of  from 
one  to  two  minutes,  so  as  to  form 
a  saturated  solution.  Note  the 
temperature  of  the  solution. 

Accurately  weigh  a  small 
evaporating-dish  and  watch-glass 
cover;  then  filter  into  the  dish 
about  20  cc.  of  the  saturated  solu- 
tion of  salt  and  reweigh.  Eemove 
the  watch-glass  and  place  the 
dish  in  a  beaker  partially  filled  with  water  as  shown  in 
Fig.  33.  Keep  the  water  in  the  beaker  boiling.  The  resulting 

40 


FIG.  33 


steam  heats  the  dish  and  causes  the  water  in  the  dish  to 
evaporate.  After  the  solution  has  evaporated  to  dryness, 
cover  the  dish  with  the  watch-glass  and  heat  it  directly 
with  the  burner,  regulating  the  flame  so  that  the  tip  barely 
touches  the  dish.  Continue  the  heating  until  all  the  mois- 
ture has  been  expelled  and  the  under  part  of  the  watch-glass 
is  free  from  moisture.  (Why  use  the  watch-glass  cover  ? ) 

Now  withdraw  the  burner,  and  after  the  dish  is  cool 
(room  temperature)  weigh  once  more.  From  your  results 
calculate  the  approximate  number  of  grams  of  salt  that  will 
dissolve  in  1  liter  of  water  at  the  temperature  of  the  origi- 
nal solution. 

6.  If  time  permits,  the  solubility  of  other  substances  such 
as  calcium  sulfate  and  potassium  dichromate  may  be  deter- 
mined in  like  manner;  or  different  students  may  select 
different  substances  and  compare  their  results. 

EXERCISE  24 

*A  METHOD  FOR  DETERMINING  WHETHER  OR  NOT  A 
GIVEN  LIQUID  IS  A  CONDUCTOR  OF  ELECTRICITY 

Apparatus.  Apparatus  as  shown  in  Fig.  34  (p.  153  of  text) ;  cur- 
rent from  electric-lighting  system. 

Materials.  5  g.  common  salt ;  5  g.  sugar ;  5  cc.  sodium  hydroxide 
solution  added  to  20  cc.  water ;  3  cc.  sulf  uric  acid  added  to  20  cc. 
water ;  tap  or  well  water. 

a.  Obtain  from  your  instructor  the  apparatus  shown  in 
Fig.  34.  Polish  the  copper-wire  electrodes  with  emery  paper 
until  they  are  bright  and  free  from  oxide.  At  the  beginning 
of  each  experiment  see  that  the  electrodes  are  bright  and  dry, 
and  that  the  cell  is  also  perfectly  clean.  Unscrew  a  lamp  C 
from  a  convenient  socket  above  your  desk,  screw  it  loosely 
into  the  socket  on  your  apparatus,  and  attach  the  apparatus 
to  the  empty  socket  on  the  lighting  system  by  means  of 
the  extension  cord  and  plug  B.  Every  time  a  change  is  to 

41 


be  made  in  the  cell,  loosen  the  lamp  in  the  socket,  and 
do  not  screw  it  down  to  make  contact  until  all  of  the  con- 
nections of  the  cell  have  been  arranged. 

b.  Partly  fill  the  cell  A  with  dry  powdered  salt,  dip  the 
electrodes  into  the  powder,  arrange  the  connections  at  the 


FIG.  34 

binding-posts,  and  screw  down  the  lamp  C.    Does  the  salt 
conduct  the  electric  current  ? 

c.  Eepeat  ft,  using  distilled  water  (?). 

d.  Eepeat  b,  using  a  solution  of  the  salt  in  distilled  water  (?). 

e.  Test  the  conductivity  of  the  following  substances  and 
interpret  the  results :  (1)  dry  powdered  sugar ;  (2)  a  solu- 
tion of  sugar  in  water ;  (3)  tap  or  well  water ;  (4)  distilled 
water  containing  a  few  drops  of  sulfuric  acid ;  (5)  a  solution 
of  sodium  hydroxide. 


42 


EXERCISE  25 


THE   PREPARATION   AND    PROPERTIES  OF    CHLORINE 

Apparatus.  Apparatus  as  shown  in  Fig.  35  (A  is  a  250-cc.  flask 
and  B  and  C  250-cc.  bottles ;  B  contains  some  sulfuric  acid)  ;  4 
additional  250-cc.  bottles  (dry)  ;  glass  plates ;  200-cc.  beaker  with 
glass  plate  cover. 

Materials.  25  g.  manganese  dioxide ;  hydrochloric  acid ;  bit  of 
powdered  antimony;  strip  of  copper  foil;  strips  of  colored  calico; 
piece  of  printed  paper  (printer's  ink)  ;  paper  written  over  with 
ordinary  ink ;  1  g.  potassium  permanganate. 

PRECAUTION.  All  of  the  following  experiments  must  be  performed 
in  the  hood,  and  great  care  must  be  taken  not  to  inhale  the  chlorine. 

a.  (Two  students  may  work  together.)  Arrange  an  appa- 
ratus according  to  Fig.  35.  Put  into  the  flask  from  20  to 
25  g.  of  manganese 
dioxide.  Insert  the 
cork  and  pour  150  cc. 
of  hydrochloric  acid 
through  the  funnel 
tube.  Shake  the  flask 
so  as  to  mix  the 
contents  thoroughly. 
Warm  gently,  apply- 
ing just  enough  heat 
to  cause  a  gentle 
evolution  of  the  gas, 
but  not  sufficient  to 
boil  the  liquid.  The  FlG>  35 

chlorine      generated 

bubbles  through  the  sulfuric  acid  in  B  (which  removes  the 
moisture)  and  is  collected  in  C.  Fill  four  bottles  with  the 
gas  (note  the  color),  cover  them  with  glass  plates,  and  set 
them  aside. 

43 


b.  Grind  a  fragment  of  antimony  to  a  fine  powder  and 
sprinkle  a  pinch  of  the  powder  into  one  of  the  bottles  of 
the  gas.    SbCl3  is  formed  (R). 

c.  Support  by  forceps  a  small  piece  of  copper  foil,  heat 
it  to  redness,  and  immediately  thrust  it  into  a  bottle  of  the 
gas.    Describe  the  result.    What  is  formed  ? 

d.  Suspend  strips  of  colored  calico  in  a  bottle  of  the  dry 
gas;  also  two  strips  of  paper,  the  one  with  writing  in  ink 
on  it,  the  other  with  printing  (printer's  ink)  on  it. 

e.  Repeat  d,  using  similar  strips,  but  moistened  with  water. 
Describe  the  results  in  d  and  e.    What  part  does  the  water 
play  in  the  bleaching  ? 

/.  Place  a  few  crystals  of  potassium  permanganate  on  the 
bottom  of  a  clean  beaker.  Pour  over  these  3  cc.  of  hydro- 
chloric acid  and  cover  the  beaker  with  a  glass  plate.  Ex- 
amine after  a  few  minutes  and  test  (?)  the  gas  in  the  beaker 
for  the  presence  of  chlorine  (?) . 

EXERCISE  26 

THE  PREPARATION  AND  PROPERTIES  OF  HYDROGEN 
CHLORIDE  AND  OF  HYDROCHLORIC  ACID 

Apparatus.  Flask  and  bottle  connected  as  shown  in  Fig.  36  (this 
is  same  as  shown  in  Fig.  35,  except  that  the  glass  tube  extending 
into  the  bottle  B  ddes  not  touch  the  liquid  (water)  in  B)  ;  two  250- 
cc.  bottles  (dry)  ;  burner ;  large  beaker. 

Materials.  Dilute  sulfuric  acid  prepared  by  slowly  pouring  (3  or 
4  drops  at  a  time  with  constant  stirring)  30  cc.  of  the  concentrated 
acid  into  10  cc.  water;  50  g.  sodium  chloride;  splint;  blue  litmus 
paper. 

a.  Usual  laboratory  method  of  preparation.  Put  about 
50  g.  of  common  salt  into  the  generator  flask  (Fig.  36), 
insert  the  cork,  pour  the  cold  dilute  sulfuric  acid  through 
the  funnel  tube,  mix  the  contents  by  a  gentle  motion  of  the 
flask,  and  after  two  or  three  minutes  warm  gently  with  a 

44 


small  flame.  Notice  the  currents  in  the  water  in  B.  What 
causes  them  ?  As  soon  as  the  gas  is  evolved  regularly,  dis- 
connect the  generator  flask  at  D  long  enough  to  collect  two 
bottles  of  the  gas  by  displacement  of  air  (as  in  Fig.  30). 
Cover  these  tightly  with  glass  plates  and  set  them  aside ; 
then  connect  the  generator  with  B  again  and  continue  to 
apply  a  gentle  heat  as  long 
as  any  gas  is  evolved  (E). 

b.  What    is   the    color   of 
the  gas  (examine  that  in  the 
generator)  ? 

c.  Test  the  gas  in  one  of 
the   bottles   with    a   lighted 
splint.   Is  it  combustible  ?  Is 
it  a  supporter  of  combustion  ? 

d.  Fill  a  large  beaker  with 
water.    Now  uncover  the  re- 
maining bottle,  invert  it,  and 
at  once  bring  its  mouth  under 
the  surface  of  the  water  in  the 
beaker.    Describe  the  results. 

What  does  the  experiment  prove?    Why  not   extend  the 
tube  in  bottle  B  (Fig.  36)  to  the  bottom  of  the  bottle  ? 

e.  Put  a  drop  of  the  aqueous  solution  of  the  acid  from 
bottle  B  on  a  bit  of  blue  litmus  paper.    Note  the  result. 
Pour  2  drops  of  the  solution  into  3  or  4  cc.  of  water  and 
taste  a  drop.    Perform  a  test-tube  experiment  to  prove  the 
presence  of  chlorine  in  the  acid  (R) ;  also  one  to  prove  the 
presence  of  hydrogen  (E).    How  does  the  solution  compare 
with  the  hydrochloric  acid  on  your  desk  ? 

/.  Distinguish    clearly   between    hydrogen    chloride   and 
hydrochloric  acid. 


FIG. 36 


45 


EXERCISE  27 

SODIUM;  SODIUM  HYDROXIDE 

Apparatus.    Evaporating-dish  with  glass-plate  cover ;  burner. 
Materials.    Bit  of  sodium,  half  as  large  as  a  pea ;  red  litmus  paper. 

Recall  experiment  a,  Exercise  8.  Obtain  from  your  in- 
structor a  bit  of  sodium.  Cut  it  and  note  the  rapidity  with 
which  the  freshly  cut  surface  is  tarnished.  Half  fill  your 
evaporating-dish  with  water;  then  drop  the  sodium  into 
this  and  quickly  cover  the  dish  with  a  glass  plate  (R).  Is 
the  sodium  heavier  or  lighter  than  water  ?  After  the  action 
has  ceased,  place  a  drop  of  the  resulting  liquid  on  a  piece  of 
red  litmus  paper.  Contrast  its  action  with  that  of  hydro- 
chloric acid  on  litmus  paper  (Exercise  26).  Mix  1  or  2  drops 
of  the  solution  with  5  cc.  of  water  and  taste  a  drop  of  the 
resulting  solution.  Contrast  with  the  taste  of  hydrochloric 
acid  (Exercise  26).  Evaporate  the  solution  to  dryness  (?). 

EXERCISE  28 

THE  PROPERTIES  OF  ACIDS,  BASES,  AND  SALTS 

Apparatus.  3  small  beakers ;  stirring-rod ;  evaporating-dish  :  ring 
stand  and  burner ;  apparatus  shown  in  Fig.  34. 

Materials.  A  few  drops  of  each  of  the  following  acids :  hydro- 
chloric, sulf uric,  nitric,  acetic  (R.  S.) ;  solutions  of  the  following  bases  : 
sodium  hydroxide,  potassium  hydroxide  (R.  S.),  calcium  hydroxide 
(R.S.)  ;  strips  of  blue  and  of  red  litmus  paper;  *  10  cc.  solution  of 
hydrogen  chloride  in  benzene. 

a.  Recall  the  properties  of  hydrochloric  acid  (Exercise  26). 
Prepare  a  dilute  solution  of  each  of  the  following  acids  by 
adding  1  or  2  drops  of  the  acid  to  10  cc.  of  water:  hydro- 
chloric, sulfuric,  nitric,  acetic. 

By  means  of  a  clean  glass  rod  transfer  a  drop  of  each  to 
a  piece  of  blue  litmus  paper.  Note  the  result.  In  a  similar 

46 


way  try  their  effect  on  red  litmus  paper.  Taste  one  drop  of 
the  dilute  solutions  (rinse  the  mouth  with  water  after  tasting). 
Determine  whether  or  not  the  solutions  conduct  the  electric 
current,  using  the  method  employed  in  Exercise  24. 

Compare  the  formulas  of  the  acids.  In  what  respect  are 
the  acids  similar  in  composition  ? 

b.  In  a  similai-  way  try  the  effect  on  red  litmus  paper  of 
a  solution  of  each  of  the  following  bases :  sodium  hydroxide 
(recall  Exercise  27),  potassium  hydroxide,  calcium  hydroxide. 
Do  they  affect  the  blue  litmus  paper?    Taste  a  drop  of  the 
calcium  hydroxide  solution.    Determine  whether  or  not  the 
solutions   conduct  the  electric  current,  using  the  method 
employed  in  Exercise  24. 

Compare  the  formulas  of  the  bases.  In  what  respect  are 
the  bases  similar  in  composition  ? 

c.  Dilute   5   cc. ,  of   the   ordinary  laboratory  solution    of 
sodium  hydroxide  (1  part  of  the  hydroxide  to  10  parts  of 
water)  with  an  equal  volume  of  water.    To  this  solution 
add  4  or  5  drops  of  hydrochloric  acid  (K).    Stir  the  resulting 
solution  with  a  glass  rod  and  test  its  action  on  blue  and  on 
red  litmus  paper.    Has  it  acid  or  basic  properties  ? 

Now  continue  to  add  the  acid  drop  by  drop  until  the 
resulting  solution  is  neutral  (that  is,  has  no  effect  on  either 
blue  or  red  litmus  paper)  or  is,  at  most,  slightly  acid.  Pour 
the  solution  into  an  evaporating-dish  and  evaporate  to  dryness. 
What  compound  remains  ?  Taste  it. 

What  is  the  name  given  to  the  compounds  formed  by  the 
interaction  of  acids  and  bases  ? 

*d.  Obtain  from  your  instructor  10  cc.  of  a  solution  of 
hydrogen  chloride  in  benzene.  Does  it  conduct  the  electric 
current  (?)  ?  Try  its  action  on  litmus  paper  (?) ;  on  zinc  (?). 
Account  for  the  results. 

e.  Characterize  acids  and  bases  (1)  as  to  composition,  (2) 
as  to  their  action  on  litmus,  (3)  as  to  taste,  (4)  as  to  their 
conductivity,  (5)  as  to  their  interaction  with  each  other. 

47 


EXERCISE  29 


THE  RATIO  OF  ACID  TO  BASE  IN  NEUTRALIZATION 
(QUANTITATIVE) 

Apparatus.  2  burettes  and  supports,  as  shown  in  Fig.  37 ;  small 
beaker  and  stirring-rod. 

Materials.  Sodium  hydroxide  solution  prepared  by  adding  20  cc. 
of  the  laboratory  reagent  to  100  cc.  water ;  1  cc.  sulf uric  acid  added 
to  100  cc.  water ;  a  few  drops  of  a  phenolphthalein  solution  (R.  S.). 

(Two  students  may  work  together.) 

Kinse  out  a  burette,  first  with  distilled  water  and  then 
with  a  little  of  the  solution  of  sodium  hydroxide.  Support 
the  burette,.  (Fig.  37),  and  pour  into  it 
the  hydroxide  solution  until  the  level 
of  the  liquid  is  1  or  2  cm.  above  the 
zero  mark.  Turn  the  stopcock  and  let 
the  solution  flow  out  until  the  bottom 
of  the  curved  surface  (meniscus)  of  the 
liquid  in  the  burette  is  on  a  level  with 
the  zero  mark.  In  a  similar  way  fill  a 
second  burette  with  the  acid  solution. 

Now  let  exactly  15  cc.  of  the  acid 
solution  flow  into  a  small  beaker,  add 
two  drops  of  phenolphthalein  solution, 
and  run  in  2  or  3  cc.  of  the  hydroxide 
solution.  Notice  that  where  the  liquids 
come  in  contact  a  reddish  color  is  pro- 
duced, which  disappears  quickly  on 

stirring.  Eun  in  more  of  the  solution,  a  little  at  a  time,  until 
the  color  fades  slowly,  and  then  a  drop  at  a  time  until  the 
entire  liquid,  on  stirring,  remains  colored  faintly  pink.  This 
marks  approximately  the  point  of  neutralization.  Note  the 
number  of  cubic  centimeters  of  the  hydroxide  solution  used. 

48 


FIG.  37 


Repeat  the  experiment,  using  different  volumes  of  acid, 
say  10  cc.  and  20  cc.  Calculate  in  each  case  the  number  of 
cubic  centimeters  of  the  hydroxide  solution  required  to 
neutralize  1  cc.  of  the  acid  solution.  What  do  the  results 
prove  ? 

EXERCISE  30 

THE  DISPLACEMENT  OF  METALS  FROM  THEIR 
COMPOUNDS 

Apparatus.    4  test  tubes ;  test-tube  rack. 

Materials.  4  strips  each  of  zinc  and  copper  (1  cm.  X  10  cm.) ;  0.5  g. 
lead  nitrate  dissolved  in  10  cc.  water ;  0.5  g.  copper  nitrate  dissolved 
in  10  cc.  water ;  0.5  g.  mercuric  nitrate  dissolved  in  10  cc.  water ;  3  cc. 
sulfuric  acid  dissolved  in  10  cc.  water. 

a.  Pour  into  separate  test  tubes  to  a  depth  of  4  or  5  cm. 
solutions    of   the    following   compounds :    (1)    lead   nitrate, 
(2)   dilute   sulfuric   acid,   (3)    copper   nitrate,   (4)   mercuric 
nitrate.    Set  the  tubes  in  a  rack  in  the  order  given  above 
and  label  them  "A,"  "  B,"  "  C,"  and  "  D  "  respectively. 

Now  place  in  each  tube  a  strip  of  zinc.  (It  is  convenient  to 
have  a  strong  thread  attached  to  the  upper  part  of  each  strip 
so  that  the  strip  may  easily  be  withdrawn  from  the  tube.) 
Note  any  change  taking  place  in  the  appearance  of  the  zinc. 

After  from  twenty  to  thirty  minutes  withdraw  the  strips 
and  wipe  them  carefully  on  a  piece  of  white  paper.  Note  any 
evidence  tending  to  show  that  the  zinc  has  displaced  the 
lead,  hydrogen  (p.  191  of  text),  copper,  and  mercury  from 
their  salts.  Has  the  solution  of  copper  nitrate  faded  in  color  ? 
(Metals  in  a  very  finely  divided  form  are  black,  as  a  rule.) 

b.  Repeat  experiment  a,  substituting  for  the  zinc  a  strip 
of  copper.    Contrast  the  results  obtained  with  those  obtained 
in  a.  How  do  you  account  for  the  change  in  the  color  of  the 
solution  of  mercuric  nitrate  after  the  addition  of  the  copper 
strip  ?    Are  your  results  in  accord  with  the  displacement- 
series  table  given  on  page  191  of  text? 

49 


EXERCISE  31 


*THE  DETERMINATION  OF  THE  AMOUNT  OF  HYDROGEN 

DISPLACED  BY  A  DEFINITE  WEIGHT   OF    DIFFERENT 

METALS  (QUANTITATIVE) 

Apparatus.  Apparatus  shown  in  Fig.  38  (the  bottle  B  and  fittings 
are  the  same  as  used  in  Exercise  12  (Fig.  25)). 

Materials.  About  1  g.  granulated  zinc ;  dilute  sulfuric  acid  pre- 
pared by  adding  10  cc.  concentrated  acid  to  30  cc.  water ;  dilute 
hydrochloric  acid  prepared  by  adding  20  cc.  of  the  concentrated  acid 
to  20  cc.  water. 

(Two  students  work  together.  Some  should  use  sulfuric 
acid  as  the  solvent  and  others  hydrochloric  acid,  so  that 
the  results  may  be  compared.  The  apparatus  is  not  diffi- 
cult to  prepare  and  gives 
excellent  results.) 

Arrange  an  apparatus 
in  accordance  with  Fig.  38. 
A  is  a  60-cc.  wide-mouthed 
bottle.  The  bottle  B  and 
accompanying  tubes  are 
the  same  as  shown  in 
Fig.  25  except  that  the 
hard-glass  test  tube  has 
been  removed.  The  glass 
tube  G  is  drawn  out  to 
a  jet  at  the  lower  end,  FIG  3g 

and  the  other  end  is  con- 
nected to  the  funnel  H  by  means  of  a  rubber  tube  which 
can  be  closed  by  the  screw  clamp  /.    The  bottles  A  and  B 
are  joined  by  a  rubber  tube  K. 

Disconnect  the  bottles  A  and  B  at  K  and  fill  the  bottle 
B  and  the  exit  tube  C  E  with  water,  as  in  Exercise  12, 
and  tightly  close  the  screw  clamp  D. 

50 


Weigh  out  accurately  about  1  g.  of  zinc.  Wind  a  piece  of 
platinum  wire  (used  in  place  of  copper  sulfate  solution)  about 
the  zinc,  place  it  in  the  bottle  A,  and  set  the  bottle  aside. 

Close  the  screw  clamp  /  and  nearly  fill  the  funnel  with  the 
dilute  sulfuric  acid.  Place  a  beaker  under  the  tube  G  and 
open  the  screw  clamp  /  until  the  rubber  and  the  glass  tubes 
are  both  completely  filled  with  the  dilute  acid ;  then  quickly 
close  the  clamp.  Next,  connect  the  apparatus  just  as  shown 
in  the  figure,  taking  care  to  make  the  apparatus  air-tight. 

Now  adjust  the  pressure  of  the  air  inside  the  bottles  to 
atmospheric  pressure,  just  as  directed  in  Exercise  12. 

Next,  open  the  clamp  D,  then  partially  open  the  clamp  / 
and  allow  8  or  10  drops  of  the  acid  to  flow  into  the  bottle 
A.  The  hydrogen  evolved  forces  the  water  from  bottle  B 
into  the  beaker.  If  necessary,  more  acid  is  added  from  time 
to  time  until  the  zinc  is  dissolved.  After  the  zinc  has  all 
dissolved  and  the  apparatus  has  acquired  the  room  temper- 
ature, again  adjust  the  pressure  of  the  gas  within  the  bottles 
to  the  atmospheric  pressure  and  close  the  clamps  D  and  /. 

Insert  the  values  in  the  table  below: 

Weight  of  metal  taken g. 

Volume  of  water  forced  into  the  beaker  F  .     .     .         cc. 

Volume  of  liquid  left  in  bottle  A cc. 

Volume  of  hydrogen  liberated  =  volume  of  water 

in  F  less  volume  of  liquid  in  A cc. 

Temperature •••/ 

Barometric  reading  .     .     .     .     .     .     .     .   ' .  • .  7s  .    .     mm. 

Value  of  vapor  pressure  (Appendix)   .     .     .     .     .         mm. 

Volume  that  the  hydrogen  would  occupy  under 

standard  conditions cc. 

Weight  of  this  volume  of  hydrogen  (1  liter  H  = 

.089879)       ,     .  : g- 

Weight  of  hydrogen  liberated  by  1  g.  of  zinc  .     .         g. 

Compare  the  results  obtained  by  the  students  using  sul- 
furic acid  as  the  solvent  with  the  results  obtained  by  using 
hydrochloric  acid  as  the  solvent  (?). 

51 


EXERCISE  32 
THE  PREPARATION  AND  PROPERTIES  OF  AMMONIA 

Apparatus.  Test  tube ;  hard-glass  test  tube  fitted  with  cork  and 
tubing  as  shown  in  Fig.  39 ;  ring  stand  and  burner ;  three  250-cc. 
wide-mouthed  bottles ;  piece  of  window  glass ;  piece  of  cardboard. 

Materials.  Solution  of  sodium  hydroxide ;  9  g.  ammonium  chlo- 
ride ;  15  g.  powdered  slaked  lime  (slaked  or  hydrated  lime,  Ca(OH)2)  ; 
red  litmus  paper ;  5  cc.  red  litmus  solution  prepared  by  heating  a  bit 
of  litmus  in  water  and  filtering. 

a.  Dissolve  0.5  g.  of  ammonium  chloride  in  3  or  4  cc.  of 
water  in  a  test  tube  and  heat  to  boiling.  Note  the  odor  (?). 

Now  add  5  cc.  of  a  solution  of  sodium  hydroxide  to  the 
hot  solution  of  ammonium  chloride  and  continue  the  heat- 
ing. Again  note  the  odor  (?).  Moisten  a  strip  of  red  litmus 
paper  and  hold  it  at  the  mouth  of  the  tube  but  not  in 
contact  with  it  (?). 

Dip  the  end  of  a  glass  rod  in  a  concentrated  solution  of 
hydrochloric  acid  and  hold  it  in  the  mouth  of  the  test 
tube  (?). 

Complete  the  following  equations : 


NH4OH  +  HC1 >- 

b.  Usual  laboratory  method  for  preparing  ammonia.  This 
differs  from  the  method  used  in  a  only  in  the  fact  that  the 
less  expensive  calcium  hydroxide  (slaked  lime)  is  substituted 
for  the  sodium  hydroxide.  The  form  of  apparatus  used  is 
shown  in  Fig.  39.  The  bottle  B  (250-cc.)  contains  25  cc. 
of  water.  The  glass  tube  C  extends  through  a  hole  in  a 
cardboard  resting  on  the  mouth  of  the  bottle.  The  end  of 
the  tube  must  just  touch  the  water  in  the  bottle. 

52 


Place  in  the  tube  A  a  mixture  of  1 5  g.  of  powdered  slaked 
lime  and  8  g.  of  ammonium  chloride.  Connect  the  tube  as 
shown  in  Fig.  39  and  heat  the  mixture  gently,  beginning 
with  that  portion  near  the  mouth  of  the  tube  and  gradually 
extending  the  heat  to  the  other  portions.  As  soon  as  the 
gas  is  evolved  freely  (as  shown  by  the  bubbles  at  the  end 
of  the  tube  (7),  bring  the  tube  C  to  an  upright  position,  as 

shown  in  the  dotted  1 

lines,  and  collect  two 

!         n         ! 

bottles  of  the  gas  by 
upward  displacement. 
To  do  this,  bring 
each  bottle  succes- 
sively down  over  the 
exit  tube  and  hold 
in  this  position  until 
a  drop  of  hydrochloric 
acid  on  the  end  of 
a  glass  rod  fumes 
strongly  when  held 
at  the  mouth  of  the 
bottle  (?) ;  then  withdraw  the  bottle,  cover  its  mouth  with 
a  glass  plate,  and  set  it  aside,  mouth  downward  (?). 

When  both  bottles  are  filled,  bring  the  tube  C  into  the 
bottle  B  again  and  continue  to  heat  the  mixture  gently  as 
long  as  any  gas  is  generated.  Write  the  equations  for  all 
the  reactions  involved. 

c.  Note  the  color  and  odor  (caution}  of  the  gas.    Is  it 
heavier  or  lighter  than  air  ? 

d.  Test  a  bottle  of  the  gas  with  a  burning  splint.    Describe 
the  results. 

e.  Fill  a  large  beaker  with  water  and  color  it  with  a  few 
drops  of  red  litmus  solution.    Uncover  the  remaining  bottle 
of  the  gas  and  at  once  bring  its  mouth  under  the  surface  of 
the  water  in  the  beaker.    Leave  it  in  this  position  for  five 

53 


O   I 

. 

C 

\ 

/ 

«r— 

J 

I 

=1 

^=^ 

& 

- 

as 

FIG.  39 


minutes,  taking  care  to  keep  the  mouth  of  the  bottle  below 
the  surface  of  the  water.    What  do  the  results  prove  ? 

/.  Note  the  odor  of  the  liquid  in  the  bottle  B.  Try  its 
effect  on  blue  and  on  red  litmus  paper.  How  does  it  com- 
pare with  the  aqua  ammonia  of  the  druggist  in  its  odor  and 
its  action  on  litmus  ?  Does  the  gas  combine  with  the  water, 
or  is  it  simply  dissolved  in  the  water  ?  Give  reasons  for 
your  answer.  Now  neutralize  the  liquid  with  hydrochloric 
acid  (E)  and  evaporate  just  to  dryness.  Compare  the  residue 
with  the  ammonium  chloride  used  in  experiment  a. 

EXERCISE  33 
THE  PREPARATION  AND  PROPERTIES  OF  NITRIC  ACID 

Apparatus.  Glass  retort  (150-cc.),  test  tube,  and  beaker  (500-cc.), 
arranged  as  shown  in  Fig.  40 ;  funnel ;  evaporating-dish  ;  ring  stand 
and  burner. 

Materials.  12  g.  sodium  nitrate ;  10  cc.  sulfuric  acid  ;  small  piece 
of  tin ;  small  strip  of  copper ;  pieces  of  ice,  size  of  walnut. 

fl.  Arrange  an  apparatus  like  that  shown  in  Fig.  40.  Put 
in  the  retort  A  about  12  g.  of  sodium  nitrate  and  10  cc.  of 
sulfuric  acid,  pouring  the  latter  through  a  funnel  placed  in 
the  tubulus  B  of  the  retort.  Heat  the  mixture  gently  with 
a  small  flame.  Nitric  acid  is  set  free  (E),  distills  over,  and 
is  condensed  in  the  test  tube  C,  which  is  kept  cold  by  being 
partly  immersed  in  ice  water  in  the  beaker  D.  Convince 
yourself  that  it  is  an  acid  (?). 

b.  When  nitric  acid  is  heated  a  part  of  it  is  decomposed 
into  water,  nitrogen  dioxide,  and  oxygen  (E).  On  this  account 
it  is  a  good  oxidizing  agent.  To  test  its  oxidizing  properties, 
put  a  small  piece  of  tin  in  a  test  tube,  cover  it  with  a  little 
nitric  acid,  and  gently  heat  (hood).  The  white  residue  formed 
is  composed  mainly  of  tin  and  oxygen,  the  latter  being 
supplied  by  the  nitric  acid. 

54 


B 


Pure  nitric  acid  is  colorless.    How  do  you  account  for  the 
color  of  the  acid  which  you  have  prepared  ? 

c.  Place  a  small  strip  of  copper  in  an  evaporating-dish 
(hood)  and  add  some  of  the  acid  you  have  prepared, 
a  few  drops  at  a 
time,  until  the  cop- 
per is  just  dissolved. 
Evaporate  the  solu- 
tion to  dryness 
(Fig.  33).  Note  the 
appearance  of  the 
residue.  Since  cop- 
per is  below  hydro- 
gen in  the  displace- 
ment series,  how  do 
you  account  for  the  • 

fact  that  nitric  acid  dissolves  the  metal  (study  the  reaction 
on  page  212  of  text)?  Save  the  residue  in  the  dish  (what 
is  it?)  for  use  in  the  following  experiment. 


FIG.  40 


EXERCISE  34 

THE  PROPERTIES  OF  THE  SALTS  OF  NITRIC  ACID 
(NITRATES) 

Apparatus.  Evaporating-dish  containing  the  copper  nitrate  pre- 
pared in  Exercise  33 ;  5  test  tubes  in  test-tube  rack. 

Materials.  Strip  of  copper;  crystal  of  lead  nitrate;  crystals  of 
such  nitrates  as  are  available;  sulfuric  acid;  2  g.  ferrous  sulfate 
dissolved  in  10  cc.  water. 

a.  Heat  the  dish  (hood)  containing  the  copper  nitrate,  pre- 
pared in  Exercise  33,  with  a  small  flame.    Note  the  color  of 
the  gas  evolved,  also  the  color  of  the  residue  (?).    Compare 
the  residue  with  a  sample  of  copper  oxide. 

b.  Place  a  crystal  of  lead  nitrate  in  the  evaporating-dish 
and  heat  gently.    Compare  with  the  results  obtained  in  a. 

55 


c.  Place  a  small  crystal  of  such  nitrates  as  are  availa- 
ble in  your  laboratory  in  separate  test  tubes  and  test  their 
solubility  in  water.    What  nitrates  are  insoluble  in  water 
(p.  394  of  text)  ? 

d.  How  to  detect  the  presence  of  nitrates.  Dissolve  a  crystal 
of  sodium  nitrate  in  2  or  3  cc.  of  water  in  a  test  tube,  care- 
fully add  (recall  experiment  b,  Exercise  8)  an  equal  volume  of 
sulf  uric  acid,  mix,  and  cool  to  room  temperature  or  below.  The 
sulfuric  acid  acts  on  the  nitrate,  liberating  nitric  acid.    Now 
tip  the  tube  slightly  and  gently  pour  2  or  3  cc.  of  the  solution 
of  ferrous  sulfate  down  the  side  of  the  tube,  so  that  it  floats 
on  the  heavier  liquid,  and  set  the  tube  aside,  being  careful 
not  to  mix  the  two  liquids.    A  brown  ring  soon  forms  where 
the  liquids  meet.    Eepeat  the  experiment,  using  potassium 
nitrate.    This  is  a  good  test  for  nitrates.    The  brown  ring  is 
due  to  the  presence  of  a  complex  compound  formed  by  the 
action  of  ferrous  sulfate  on  nitric  acid. 

EXERCISE  35 

THE  PREPARATION  AND  PROPERTIES  OF  SOME  OF 
THE  OXIDES  OF  NITROGEN 

Apparatus.  Hard-glass  test  tube,  with  delivery  tube,  as  used  in 
preparing  oxygen  (Fig.  20) ;  3  wide-mouthed  bottles  (250-cc.) ;  pneu- 
matic trough;  hydrogen  generator  (Fig.  21). 

Materials.  8  g.  ammonium  nitrate  ;  wooden  splints ;  5  small  strips 
of  copper ;  10  cc.  nitric  acid. 

a.  Nitrous  oxide.  Put  6  or  8  g.  of  ammonium  nitrate  in 
the  hard-glass  test  tube  used  in  the  preparation  of  oxygen. 
Attach  a  delivery  tube  and  heat  gently,  applying  no  more 
heat  than  is  necessary  to  cause  a  slow  evolution  of  the  gas. 

As  soon  as  the  gas  is  regularly  evolved,  collect  two  or 
three  bottles  of  it  over  water.  Notice  the  water  deposited 
on  the  sides  of  the  test  tube.  What  is  the  source  of  it? 
Note  the  color,  odor,  and  taste  of  the  gas.  Test  it  with  a 

56 


glowing  splint.  Account  for  the  result.  How  can  you 
distinguish  between  nitrous  oxide  and  oxygen  ? 

b.  Nitric  oxide  and  nitrogen  dioxide.  Put  a  few  pieces  of 
copper  in  your  hydrogen  generator  (hood),  just  cover  them 
with  water,  and  add  2  or  3  cc.  of  nitric  acid.  Collect  over 
water  two  bottles  of  the  evolved  gas,  adding  more  nitric  acid 
to  the  liquid  in  the  generator  if  necessary. 

Compare  the  color  of  the  gas  in  the  generator  with  that 
collected  in  the  bottles  and  account  for  any  difference. 
Write  the  equations  for  all  the  reactions  involved. 

Uncover  one  of  the  bottles  of  the  gas  and  account  for  the 
result  (E).  Test  the  gas  in  the  second  bottle  with  a  burning 
splint.  Which  is  the  more  stable,  nitrous  oxide  or  nitric 
oxide  ?  Give  reasons  for  your  answer. 

EXERCISE  36 

SPEED  OF  REACTIONS;  EQUILIBRIUM;  HYDROLYSIS 

Apparatus.    6  test  tubes ;  test-tube  rack. 

Materials.  Hydrochloric  acid;  ammonium  molybdate  solution 
(R.  S.).  Silver  nitrate  solution  (R.  S.)  ;  0.1  g.  sodium  phosphate  ; 
crystal  of  sodium  chloride  dissolved  in  5  cc.  water ;  0.3  g.  of  each  of 
the  following  salts  dissolved  in  separate  portions  (3  cc.)  of  water : 
potassium  nitrate,  common  salt,  borax,  sodium  carbonate,  alum. 

a.  Speed  of  a  reaction.  Add  2  drops  of  hydrochloric  acid 
to  3  cc.  of  water  and  mix  the  two  liquids ;  then  add  1  or  2 
drops  of  a  solution  of  silver  nitrate.  Is  a  precipitate  formed 
at  once  ?  Does  the  precipitate  appear  to  increase  on  standing  ? 

Dissolve  a  crystal  of  sodium  phosphate  the  size  of  a  grain 
of  wheat  in  10  cc.  of  water  and  add  5  cc.  of  a  solution  of 
ammonium  molybdate.  Is  a  precipitate  formed  at  once  ? 
Set  the  tube  aside  until  the  end  of  the  laboratory  period, 
noting  its  appearance  from  time  to  time.  Contrast  the 
results  with  those  obtained  by  the  addition  of  silver  nitrate 
to  hydrochloric  acid. 

57 


b.  factors  affecting  speed  of  a  reaction.    Recall,  from  ex- 
periments already  performed,  the  effect  of  temperature  ;  also 
of  concentration  upon  the  speed  of  a  reaction. 

c.  Reversible   reactions.     What   is   meant   by   a   reversible 
reaction?    The  reaction  used   in  the   preparation   of   nitric 
acid  (Exercise  33)  is  reversible.     How  can   it  be  made  to 
complete  itself? 

Repeat  the  first  part  of  experiment  a,  substituting  a  solu- 
tion of  potassium  nitrate  for  that  of  silver  nitrate  (?).  The 
potassium  nitrate  acts  upon  the  hydrochloric  acid  just  as  the 
silver  nitrate  does.  In  the  former  case,  however,  the  reaction 
eoon  comes  to  an  equilibrium  while  in  the  latter  it  goes  to 
practical  completion.  Explain. 

Recall  the  process  of  neutralization.  To  what  extent  are 
such  reactions  completed  reactions  ? 

d.  Hydrolysis.  Pour  into  separate  test  tubes  small  amounts 
of  solutions  of  (1)  potassium  nitrate,  (2)  sodium   chloride, 
(3)  borax  (p.  380  of  text),  (4)  sodium  carbonate  (p.  403  of 
text),  (5)  alum  (p.  459  of  text).    Test  the  action  of  each  on 
blue  and  on  red  litmus  paper,  note  the  results,  and  explain. 

EXERCISE  37 

THE  PROPERTIES  OF  SULFUR 

Apparatus.  3  test  tubes;  smallest-sized  beaker ;  magnifying  glass ; 
porcelain  crucible ;  ring  stand  and  burner ;  large  beaker. 

Materials.  5  cc.  carbon  disulfide ;  20  g.  powdered  sulfur ;  strip  of 
copper ;  5  g.  iron  powder. 

a.  Examine  the  physical  properties  of  a  piece  of  brimstone. 
Pour  2  or  3  cc.  of  carbon  disulfide  (hood)  (keep  carbon  disul- 
fide away  from  flame  and  do  not' inhale  the  vapor)  over  3  g. 
of  powdered  brimstone  in  a  test  tube.  Cover  the  mouth  of 
the  tube  with  the  thumb  and  shake  the  contents  gently 
until  the  sulfur  is  dissolved,  adding  more  carbon  disulfide  if 
necessary.  Pour  the  clear  solution  into  a  small  beaker,  cover  it 

58 


loosely  with  a  filter  paper,  and  set  it  aside  in  the  hood.  The 
carbon  disulfide  soon  evaporates,  the  sulfur  being  deposited 
in  crystals.  Examine  these  with  a  magnifying  glass  (?). 

b.  Half  fill  a  test  tube  with  powdered  brimstone  and  heat 
it  gently  until  the  sulfur  is  just  melted.    Note  the  properties 
of  the  liquid. 

Now  apply  a  stronger  heat  and  observe  that  the  liquid 
becomes  darker  and  at  a  certain  temperature  (200°-250°) 
is  so  thick  that  the  tube  may  be  inverted  without  spilling  it. 

Finally,  increase  the  heat  until  the  sulfur  boils  (444°), 
and  then  pour  the  boiling  liquid  into  a  beaker  of  cold  water. 
Examine  the  product.  What  name  is  given  to  this  form  of 
sulfur  ?  Expose  it  to  the  air  for  an  hour.  Are  its  properties 
the  same  as  those  of  the  original  substance  ? 

c.  Fill  a  porcelain  crucible  with  powdered  brimstone  and 
apply  a  very  gentle  heat  until  the  sulfur  is  just  melted. 
Withdraw  the  flame  and   examine  the  liquid  carefully  as 
it  cools.    Crystals  soon  begin  to  form  on  the  surface  of  the 
melted   sulfur,  rapidly  extending   from   the   circumference 
toward  the  center.     Before  they  reach  the  center,  quickly 
pour  off  the   remaining  liquid   and   examine   the  crystals. 
Contrast  them  with  those  formed  in  a.    In  how  many  forms 
have  you  obtained  sulfur? 

d.  Burn  a  small  piece  of  sulfur.    Note  the  appearance  of 
the  burning  sulfur  and  the  odor  of  the  gas  formed  (?). 

e.  Boil  a  little  sulfur  in  the  test  tube  used  in  &,  and  drop 
a  small  strip  of  hot  copper  foil  into  the  boiling  liquid.     Is 
there  any  visible  evidence  of  a  chemical  change?    What  is 
formed  ? 

Grind  together  some  iron  powder  with  an  equal  weight 
of  sulfur  and  heat  the  mixture  in  a  test  tube  (?). 


59 


EXERCISE  38 


THE   PREPARATION  AND  PROPERTIES  OF  HYDROGEN 

SULFIDE 

Apparatus.  Hydrogen  generator  and  tubes,  as  shown  in  Fig.  41 ; 
2  wide-mouthed  bottles  (250-cc.  and  60-cc.) ;  funnel ;  evaporating-dish. 

Materials.  10  g.  ferrous  sulfide  ;  20  cc.  hydrochloric  acid  added  to 
20  cc.  water ;  3  cc.  nitric  acid ;  blue  and  red  litmus  paper ;  silver  coin ; 
filter  paper. 

a.  (Hood.)  Attach  a  delivery  tube  to  the  hydrogen  gen- 
erator, as  shown  in  Fig.  41.  Put  into  the  generator  A  a  few 
pieces  of  ferrous  sulfide  (FeS) 
and  insert  the  stopper.  Now 
pour  a  little  water  through 
the  funnel  tube  of  the  gener- 
ator until  the  end  of  the  tube 
just  dips  below  the  surface 
of  the  water;  then  pour  in 
a  few  cc.  of  the  hydrochloric 
acid,  adding  more  from  time 
to  time,  if  necessary,  to  main- 


o 


M 


7T 


B 


Fiu.  41 


tain  a  gentle  evolution  of  the 
gas  (R).  The  gas  escapes  into 
the  bottle  B,  which  gradually 
becomes  filled.  Note  the  odor  (CAUTION  :  the  gas  is  poisonous 
if  inhaled  in  concentrated  form)  and  color  of  the  evolved  gas. 
Continue  the  evolution  of  the  gas  until  it  is  ignited  by  a 
flame  held  at  the  mouth  of  the  bottle  B.  Account  for  the 
deposit  on  the  sides  of  the  bottle  (?). 

&.  Replace  the  bottle  B  with  a  60-cc.  bottle  half  filled 
with  water,  and  allow  the  gas  from  the  generator  (add  more 
acid  if  necessary)  to  bubble  through  the  water  for  one  or  two 
minutes.  Test  the  resulting  solution  with  blue  and  with  red 

60 


litmus  paper.  What  is  the  solution  called  ?  How  does  it 
compare  with  the  so-called  fr  sulfur  water  "  of  many  springs  ? 

Drop  a  silver  coin  into  the  solution  and  account  for  the 
results.  Why  do  certain  foods,  as  eggs,  blacken  silver  spoons  ? 

c.  Pass  a  few  bubbles  of  hydrogen  sulfide  through  3  cc.  of 
nitric  acid.  Sulfur  separates  as  a  white  solid  (?).  Account  for 
the  fact  that  sulfur  waters  deposit  sulfur  on  exposure  to  air. 

*d.  Filter  off  the  liquid  left  in  the  generator  and  evaporate 
(hood)  to  dryness  in  an  evaporating-dish.  Note  the  results. 


EXERCISE  39 

THE  PREPARATION  AND  PROPERTIES  OF  THE  SALTS 
OF  HYDROSULFURIC  ACID  (SULFIDES) 

Apparatus.  Hydrogen  generator  and  connections,  as  shown  in 
Fig.  42  ;  6  test  tubes  ;  funnel ;  watch  glass. 

Materials.  Ferrous  sulfide  and  dilute  hydrochloric  acid,  as  used 
in  Exercise  38 ;  separate  solutions  of  silver  nitrate,  copper  sulfate, 
cadmium  chloride,  lead  nitrate,  and  sodium  chloride,  made  by  dis- 
solving about  0.3  g.  of  the  solid  in  5  cc.  water  (solutions  on  reagent 
shelf  may  be  used)  ;  5  filter  papers  ;  sulfuric  acid ;  lead  acetate  (R.  S.). 


Q 


a.  Charge  the  hydrogen 
sulfide  generator  as  in  Exer- 
cise 38  and  pass  a  few  bubbles 
of  the  gas  (Fig.  42)  through 
each  of  the  following  so- 
lutions :  (1)  silver  nitrate, 
(2)  copper  sulfate,  (3)  cad- 
mium chloride,  (4)  sodium 
chloride,  (5)  lead  nitrate. 
The  exit  tube  C  through 
which  the  gas  bubbles  into 
the  solutions  must  be  thor- 
oughly cleaned  each  time  (?).  Note  the  color  of  the  pre- 
cipitates obtained.  Write  the  equations  for  the  reactions 

61 


FIG.  42 


involved.  Do  any  of  the  solutions  fail  to  give  a  precipitate 
when  the  gas  is  passed  through  them  ?  How  do  you  account 
for  this  ? 

b.  Intimately  mix  5  g.  of  sulfur  with  3  g.  of  powdered 
lime.    Transfer  to  a  beaker  and  add  150  cc.  of  water.    Stir 
the  mixture  and  heat  just  to  boiling  for  ten  minutes.    Now 
fill  a  test  tube  with  the  resulting  mixture,  cork  the  tube 
loosely,  and   set  it   aside  until  the  end  of  the  laboratory 
period;  then  examine.    Describe  the  results.    For  what  is 
the  solution  used  ?   What  is  its  composition  (p.  232  of  text)  ? 

c.  Test  for  hydrogen  sulfide.    Dip  a  strip  of  filter  paper 
into  a  solution  of  lead  acetate.    Remove  the  cork  from  the 
hydrogen  sulfide  generator  and  insert  the  paper  for  a  moment. 
Note  the  results  (E).    This  serves  as  a  convenient  test  for 
the  gas.    What  property  would  also  serve  to  detect  it  if 
present  in  any  marked  quantity  ? 

d.  Test  for  sulfides.    Filter  off  the  precipitated  sulfides 
obtained  in  a,  and  wash  them  with  water  until  the  odor  of 
hydrogen  sulfide  is  no  longer  noticeable.   Transfer  each  in 
succession  to  a  watch  glass  and  add  to  the  solid  1  or  2  drops 
of  sulfuric  acid.    Carefully  note  the  odor.    Most  of  the  sul- 
fides  when   treated   in   this  way   evolve  hydrogen   sulfide, 
which  can  be  detected  by  the  odor  and  by  its  action  on 
paper  moistened  with  lead  acetate. 

All  sulfides  when  heated  in  air  evolve  sulfur  dioxide 
(formed  by  the  combustion  of  the  sulfur  present),  which 
has  the  characteristic  odor  of  burning  sulfur.  Heat  a  little 
iron  sulfide  in  the  flame  of  the  burner  and  note  the  odor. 


62 


EXERCISE  40 


SULFUR  DIOXIDE  AND  SULFUROUS  ACID 

Apparatus.  250-cc.  flask  fitted  with  funnel  tube  and  glass  exit 
tube,  as  shown  in  Fig.  43  ;  ring  stand  and  burner ;  3  bottles  (250-cc.) ; 
2  test  tubes  ;  evaporating-dish. 

Materials.  10  g.  copper  ;  25  cc.  sulfuric  acid ;  blue  litmus  paper ; 
sodium  hydroxide  solution ;  strips  of  colored  calico  or  a  red  flower. 

a.  Preparation    of  sulfur   dioxide    and    sulfurous    acid. 
(Hood.)   Place  about  10  g.  of  copper  turnings  or  small  pieces 
of  sheet  copper  in  a  generator  arranged  as  in  Fig.  43.    Add 
25  cc.   of   concentrated    sul- 
furic acid  and  apply  a  gentle 

heat.  As  soon  as  the  action 
begins  (E),  lower  the  flame, 
regulating  it  so  as  to  obtain 
a  uniform  evolution  of  the 
gas.  Collect  two  bottles  of 
the  gas  by  displacement  of 
air;  then  cause  it  to  bubble 
through  50  cc.  of  water  as 
long  as  any  is  dissolved. 

b.  Properties.     Note     the 
odor  of  the  gas.    Is  the  gas 
combustible  ? 

Invert  one  of  the  bottles 

of  the  gas  so  that  its  mouth  is  under  water,  and  examine 
after  several  minutes  (?).    Account  for  the  results. 

Test  the  saturated  aqueous  solution  of  the  gas  with  blue 
litmus  paper.  Is  the  gas  combined  with  the  water  or  simply 
dissolved  in  it  ? 

Set  aside  10  cc.  of  the  solution  for  a  future  experiment 
(Exercise  41)  and  divide  the  remainder  into  two  equal  parts. 

63 


FIG.  43 


Immerse  in  the  one  part  some  small  strips  of  cQlored  calico 
or  some  petals  of  a  red  flower  and  note  any  results. 

c.  Salts  of  sulfurous  acid  —  the  sulfites.  To  the  remain- 
der of  the  liquid  add  a  solution  of  sodium  hydroxide,  drop 
by  drop,  until  neutral  (K),  and  evaporate  just  to  dryness. 
What  is  the  residue  ?  Moisten  it  with  2  or  3  drops  of  sul- 
furic  acid  and  note  the  odor  of  the  evolved  gas  (?).  All 
sulfites  evolve  sulfur  dioxide  when  treated  with  sulfuric  acid. 
This  reaction  serves  as  a  good  test  for  sulfites. 

EXERCISE  41 

A  STUDY  OF  SULFURIC  ACID 

Apparatus.    Burner ;  5  test  tubes. 

Materials.  Sulfuric  acid ;  2  pieces  of  granulated  zinc ;  splint ; 
0.5  g.  sugar ;  barium  chloride  solution  (R.  S.) ;  hydrochloric  acid ; 
nitric  acid ;  sulfurous  acid  prepared  in  Exercise  40 ;  bit  of  charcoal 
(size  of  a  bean). 

a.  Heat  a  bit  of  charcoal  with  1  or  2  cc.  of  sulfuric  acid. 
What  gas  is  evolved  (odor)  ?  Account  for  the  formation  of 
this  gas,  recalling  that  carbon  has  a  strong  affinity  for  oxygen. 

6.  Into  one  test  tube  pour  3  cc.  of  water  and  add  5  drops 
of  sulfuric  acid  ;  into  another  test  tube  pour  3  cc.  of  concen- 
trated sulfuric  acid.  Drop  a  small  piece  of  zinc  into  each  tube. 
If  no  reaction  takes  place,  heat  the  acid  gently.  Test  with 
a  lighted  splint  the  gas  evolved  by  the  action  of  the  dilute 
acid  on  zinc.  Note  the  odor  of  the  gas  evolved  by  the  action  of 
the  concentrated  acid  on  the  metal.  Account  for  the  difference 
in  the  action  of  the  dilute  and  the  concentrated  acid. 

c.  Put  a  drop  of  concentrated  sulfuric  acid  on  a  splint. 
Pour  a  few  drops  on  0.5  g.  of  sugar  in  a  test  tube.    Examine 
after  a  few  minutes.    Account  for  the  results. 

d.  Recall  the  action  of  sulfuric  acid  on  sodium   nitrate 
(Exercise  33).    What  property  of  sulfuric  acid  enables  it  to 
be  used  in  the  preparation  of  nitric  acid? 

64 


e.  Add  3  drops  of  sulfuric  acid  to  5  cc.  of  water  in  a  test 
tube.   To  this  add  a  few  drops  of  a  solution  of  barium  chloride. 
Note  that  a  precipitate  forms  (li).    Now  add  3  or  4  drops  of 
hydrochloric  acid.  Does  the  precipitate  dissolve  ?   The  forma- 
tion with  barium  chloride  of  a  precipitate  which  is  insoluble 
in  hydrochloric  acid  constitutes  a  good  test  for  sulfuric  acid. 

f.  Divide  the  solution  of  sulfur  dioxide  obtained  in  Exercise 
40  into  two  portions.    To  the  one,  apply  the  test  for  sulfuric 
acid  (?).  To  the  other,  add  1  cc.  of  concentrated  nitric  acid  and 
heat  gently  nearly  to  boiling ;  then  cool  and  apply  the  test  for 
sulfuric  acid  (?). 

EXERCISE  42 

SALTS  OF  SULFURTC  ACID  (SULFATES) 

Apparatus.    6  test  tubes. 

Materials.  Crystals  or  small  amounts  (0.1  g.)  of  the  sulfates  avail- 
able m  the  laboratory  ;  2  cc.  barium  chloride  solution  (R.S.)  ;  hydro- 
chloric acid. 

fl.  Examine  the  physical  properties  of  (1)  sodium  sulfate, 
(2)  calcium  sulfate,  (3)  barium  sulfate,  (4)  copper  sulfate, 
(5)  magnesium  sulfate,  (6)  ferrous  sulfate,  (7)  such  other 
sulfates  as  are  available. 

Test  the  solubility  of  each  of  the  above  sulfates  in  water. 
What  sulfates  are  insoluble  (p.  395  of  text)  ? 

b.  Prepare  a  dilute  solution  of  different  sulfates  by  dis- 
solving a  crystal  of  each  in  2  or  3  cc.  of  water.  Add  to  each 
1  drop  of  barium  chloride  solution  (?).  Add  1  or  2  drops  of 
hydrochloric  acid  to  the  mixture  in  each  tube.  Does  the 
precipitate  dissolve  ?  All  soluble  sulfates  give  in  solution  a 
white  precipitate  (BaS04)  with  barium  chloride  solution, 
which  precipitate  is  insoluble  in  hydrochloric  acid.  This 
reaction  serves  as  a  good  test  for  sulfates. 

It  will  be  noted  that  both  sulfuric  acid  and  its  salts  give 
with  barium  chloride  the  same  product;  namely,  a  white 
precipitate  of  barium  sulfate.  This  is  evident  from  the 

65 


following  facts.  It  will  be  recalled  (Chapter  XVI  of  the  text) 
that  both  acids  and  salts  are  ionized  in  solution.  In  the  case 
of  sulfuric  acid  and  sulfates,  ions  are  formed  as  follows: 

H2S04 +  H+,  H+  +  SO4-  - 

Na2SO4 )-Na+,  Na+  +  SO4~ 

.  CuS04 ^Cu++  +  S04-- 

Likewise,  barium  chloride  solution  contains  the  ions  Ba+  + 
and  Cl~,  Cl~.  Now  when  a  solution  of  barium  chloride  is 
mixed  with  any  solution  containing  the  S04~ "  ion,  the  two 
ions  Ba+  +  and  S04~~  unite  to  form  the  insoluble  BaS04, 
which  precipitates ;  hence  the  reaction  proceeds  to  comple- 
tion (p.  225  of  text).  The  barium  chloride  test  is  therefore 
really  a  test  for  the  presence  of  the  S04~  ~  ion.  Since  only 
sulfuric  acid  and  its  salts  give  this  ion,  however,  it  is  custom- 
ary to  say  that  it  is  a  test  for  sulfuric  acid  and  the  sulfates. 

EXERCISE  43 
i  HYDRATES;  EFFLORESCENCE 

Apparatus.  Burner ;  test  tubes ;  porcelain  crucible ;  ring  stand ; 
pipe-stem  triangle ;  balance  ;  evaporating-dish. 

Materials.  2  g.  zinc  sulfate  crystals ;  6  g.  copper  sulfate  crystals  ; 
clear  crystal  of  sodium  sulfate. 

a.  Hydrates.  Heat  some  small  crystals  of  zinc  sulfate  in 
a  dry  test  tube.  What  evidence  have  you  of  the  presence 
of  water  in  the  crystals  ?  Examine  the  residue.  How  does 
it  differ  from  the  original  crystals  in  form  and  composition  ? 

Select  some  small  crystals  of  copper  sulfate.  Do  they 
appear  to  be  dry  ?  Fill  a  test  tube  one-fourth  full  of  these 
crystals,  and  heat  until  no  further  apparent  change  takes 
place.  Compare  the  residue  in  form,  color,  and  composition 
with  the  original  crystals.  Dissolve  the  residue  in  as  little 
hot  water  as  possible,  pour  the  solution  (note  its  color)  into 
an  evaporating-dish,  and  set  aside  until  crystals  are  deposited. 

66 


Do  these  appear  to  be  identical  with  the  original  crystals 
of  copper  sulfate  in  shape  and  color  ? 

The  water  evolved  when  hydrates  are  heated  is  sometimes 
called  "  water  of  crystallization."  Is  the  term  appropriate  ? 
Distinguish  between  the  terms  "hydrate,"  "anhydrous," 
"  anhydride." 

b.  Efflorescence.  Expose  a  clear  crystal  of  sodium  sulfate  to 
the  air  for  one  or  two  hours.  Note  the  change  in  its  appearance. 
To  what  is  the  change  due  ?    What  are  such  bodies  called  ? 

c.  Quantitative    determination   of  the   amount  of  water 
expelled  on  heating  the  hydrate  of  copper  sulfate.    Accurately 
weigh  (or  counterpoise)  a  porcelain  crucible  and  cover.    Then 
add  2  or  3  g.   of  crystals   (no  larger  than   a  pea)   of  the 
hydrate  of  copper  sulfate  and  again  accurately  weigh.    Place 
the  covered  crucible  on  a  pipe-stem  triangle  and  heat  it 
with  a  gentle  flame  until  the  crystals  lose  their  color.    This 
will  require  from  twenty  to  thirty  minutes.    The  tip  of  the 
flame  should  not  quite  touch  the  crucible.    The  product  is 
anhydrous  copper  sulfate.    When  the  crucible  is  cool,  reweigh. 
From  your  results  calculate  the  percentage  of  water  of  crys- 
tallization present  in  the  crystals.   Compare  your  results  with 
those  obtained  by  other  members  of  the  class. 

EXERCISE  44 

THE  PREPARATION  AND  PROPERTIES  OF  HYDROGEN 
FLUORIDE 

Apparatus.  Piece  of  window  glass ;  small  lead  dish  (laboratory 
outfit). 

Materials.  2  or  3  small  pieces  of  paraffin  (size  of  a  pea);  3  g. 
fluorite;  sulfuric  acid. 

PRECAUTION.  Hydrogen  fluoride  is  very  corrosive  and  must  not  be 
inhaled ;  neither  must  its  solution  be  brought  in  contact  with  the  skin. 

Place  some  pieces  of  paraffin  on  a  glass  plate  and  gently 
warm  over  a  small  flame.  When  the  paraffin  is  melted,  tilt 

67 


the  plate  about  so  as  to  form  a  uniform  layer  of  the  wax. 
When  the  wax  is  cold,  scratch  your  name  through  the  wax 
with  a  pin.  Place  3  g.  of  fluorite  in  a  lead  dish  and  add  suffi- 
cient sulfuric  acid  to  make  a  paste  of  it.  Cover  the  dish  tightly 
with  the  waxed  side  of  the  glass  plate  and  set  it  in  the  hood 
for  an  hour;  then  scrape  off  the  paraffin  and  examine  the 
glass.  Write  the  equations  for  all  the  reactions  involved. 

EXERCISE  45 

THE  TEST  FOR  HYDROCHLORIC  ACID  AND  ITS  SALTS 
(CHLORIDES) 

Apparatus.    6  test  tubes. 

Materials.  2  cc.  silver  nitrate  solution  (R. S.);  hydrochloric  acid; 
nitric  acid ;  ammonium  hydroxide ;  crystals  of  different  chlorides, 
such  as  those  of  sodium,  calcium,  and  iron. 

NOTE.  Experiments  on  chlorine  and  hydrochloric  acid  were  in- 
cluded under  E±ercises  25  and  26.  The  student  should  carefully 
review  the  results  obtained,  since  they  have  an  important  bearing 
upon  the  experiments  now  to  be  performed  on  the  remaining 
members  of  the  Chlorine  Family. 

a.  Add  4  or  5  drops  of  hydrochloric  acid  to  4  cc.  of  water, 
mix  well,  and  add  2  or  3  drops  of  silver  nitrate  solution  (?). 

Divide  the  resulting  mixture  into  two  equal  parts :  to  the 
one  add  ammonium  hydroxide  until  the  liquid  is  alkaline  (?) ; 
to  the  other  add  2  or  3  drops  of  nitric  acid  (?). 

b.  Examine  the  physical  properties  of  such  chlorides  as 
are  available.     Test  their  solubility  in  water.    What  ones 
are  insoluble  (p.  394  of  text)?    Dissolve  a  small  crystal  of 
different  chlorides  each  in  5  cc.  of  water  and  add  silver  nitrate 
solution  as  in  a  (?).     The  formation  of  a  white  precipitate 
(AgCl)   with  silver  nitrate,  which  precipitate  is  soluble  in 
ammonium  hydroxide  and  insoluble  in  nitric  acid,  serves  as 
a  good  test  for  hydrochloric  acid  and  its  salts. 

How  do  you  account  for  the  fact  that  both  hydrochloric 
acid  and  its  salts  react  toward  silver  nitrate  in  the  same  way  ? 

68 


EXERCISE  46 

THE  PREPARATION  AND  PROPERTIES  OF  BROMINE 
AND  OF  HYDROGEN  BROMIDE 

Apparatus.  Retort,  test  tube  and  beaker,  as  shown  in  Fig.  40 ; 
burner ;  funnel ;  2  test  tubes. 

Materials.  3  g.  potassium  bromide  or  sodium  bromide ;  4  g.  man- 
ganese dioxide  ;  10  cc.  sulfuric  acid  dissolved  in  40  cc.  water;  strips 
of  colored  calico;  1  cc.  silver  nitrate  solution  (R.S.). 

PRECAUTION.  The  vapor  of  bromine  must  not  be  inhaled.  Perform 
the  experiments  in  a  hood. 

a.  Put  into  the  retort  a  mixture  of  2  g.  of  potassium  bro- 
mide or  of  sodium  bromide  and  4  g.  of  manganese  dioxide,  and 
add  to  this  through  a  funnel  a  cold  dilute  solution  of  sulfuric 
acid.  Shake  the  retort  so  as  to  mix  the  contents  thoroughly. 
The  test-tube  receiver  should  contain  sufficient  water  to 
allow  the  end  of  the  retort  to  dip  just  below  its  surface. 

Now  heat  the  retort  gently.  The  bromine  is  liberated 
and  distills  over  (E).  Continue  the  heating  until  all  the 
bromine  has  distilled  over.  Eemove  the  stopper  from  the 
retort  before  the  heat  is  withdrawn. 

6.  Note  the  properties  of  the  bromine  collected  in  the 
bottom  of  the  receiver.  Has  any  dissolved  in  the  water? 
What  property  is  implied  in  the  name  of  the  element  ? 

Test  the  bleaching  property  of  the  aqueous  solution.  How 
does  it  compare  with  chlorine  as  a  bleaching  agent? 

c.  Add  3  or  4  drops  of  sulfuric  acid  to  about  1  g.  of 
potassium  bromide  in  a  test  tube.  Some  hydrogen  bromide 
is  evolved,  which  attracts  moisture  as  it  escapes  from  the 
tube,  forming  a  light  cloud  (test  the  vapor  with  a  moist 
piece  of  blue  litmus  paper).  At  the  same  time  there  appears 
in  the  tube  a  reddish  vapor.  Explain  (p.  270  of  text). 
Distinguish  between  hydrogen  bromide  and  hydrobromic  acid. 

69 


d.  Hydrobromic  acid  is  unstable  and  is  but  little  used. 
Its  salts  (bromides)  are  stable.  Study  the  properties  of 
potassium  bromide  as  well  as  of  any  other  available  bromides. 

Dissolve  a  crystal  of  potassium  bromide  in  5  cc.  of  water 
and  apply  the  silver  nitrate  test  as  outlined  for  testing  for 
chlorides  in  Exercise  45  (?).  Would  this  test  alone  serve  to 
distinguish  between  chlorides  and  bromides  ? 

EXERCISE  47 

THE  PREPARATION  AND  PROPERTIES  OF  I,ODINE 
AND  OF  HYDROGEN  IODIDE 

Apparatus.    Retort  and  connections,  as  shown  in  Fig.  40 ;  burner. 

Materials.  4  g.  potassium  iodide  (or  sodium  iodide)  ;  4  g.  manga- 
nese dioxide;  sulfuric  acid;  chlorine  water  (R.S.);  silver  nitrate 
solution  (R.  S.)  ;  starch  solution  (R.8.);  alcohol  (R.S.). 

a.  Introduce  into  the  retort  a  mixture  of  2  g.  of  potassium 
iodide  and  4  g.  of  manganese  dioxide.    Pour  over  this  mix- 
ture 5  cc.  of  sulfuric  acid.    Insert  the  stopper  and  apply  a 
gentle  heat  (R).    Note  the  vapor  of  the  iodine  in  the  bulb  of 
the  retort;  also  note  the  grayish-black  crystals,  which  are 
soon  deposited  in  the  neck  of  the  retort.    What  property 
does  the  name  of  the  element  suggest  ? 

b.  Half  fill  two  test  tubes  with  starch  solution.    To  the 
first  add  a  few  drops  of  a  solution  of  iodine  prepared  by 
shaking  a  small  crystal  (obtained  in  a)  in  water  (?).    To  the 
second  add  a  few  drops  of  an  aqueous  solution  of  potassium 
iodide  (?).     Now  add  to  the  second  tube  2  or  3  drops  of 
chlorine  water  and  mix  the  contents  (?).    Determine  whether 
the  chlorine  water  alone   changes  the  color  of  the  starch. 
What  is  the  function  of  the  chlorine  water  added  to  the 
second  tube  ?    What  other  substance  studied  might  be  sub- 
stituted for  the  chlorine  in  this  experiment  ?  (See  Exercise  15.) 

Dissolve  a  crystal  of  iodine  in  alcohol.  What  is  the  solution 
called  ? 

70 


c.  Hydrogen  iodide  is  still  less  stable  than  hydrogen  bro- 
mide.  What  reaction  would  you  expect  to  take  place  when 
concentrated  sulfuric  acid  is  added  to  a  crystal  of  potassium 
iodide  ?    (Compare  c,  Exercise  46.)    Try  the  reaction  and  note 
any  evidences  in  favor  of  your  opinion. 

d.  The  salts  of  liydriodic  acid ;  the  iodides.    While  hydri- 
odic  acid  is  unstable,  its  salts  are  stable.    Study  the  properties 
of  potassium  iodide.    Prepare  a  solution  of  the  salt  and  study 
the  action  upon  it  of  silver  nitrate,  as  in  the  case  of  chlorides 
and  bromides. 

EXERCISE  48 

HOW  TO  DISTINGUISH  BETWEEN  CHLORIDES, 
BROMIDES,  AND  IODIDES 

Apparatus.    3  test  tubes. 

Materials.  0.2  g.  each  of  the  chloride,  the  bromide,  and  the  iodide 
of  either  potassium  or  sodium,  dissolved  separately  in  5  cc.  water ; 
5  cc.  carbon  tetrachloride  ;  chlorine  water  (R.  S.). 

fl.  Recall  the  action  of  silver  nitrate  solution  upon  solutions 
of  chlorides,  bromides,  and  iodides  (?). 

b.  Pour  the  solutions  of  the  chloride,  of  the  bromide,  and 
of  the  iodide  of  potassium  (or  sodium)  into  separate  test  tubes 
and  set  the  tubes  in  a  rack  in  the  order  given. 

Add  to  each  solution  1  cc.  of  carbon  tetrachloride  (carbon 
disulfide  will  do  as  well  but  is  inflammable).  Shake  the  con- 
tents of  the  tubes  and  set  them  aside  for  two  or  three  min- 
utes (?).  Add  to  each  tube  2  or  3  cc.  of  chlorine  water  and 
shake  again  the  contents  of  the  tubes  vigorously  and  set  aside 
for  a  few  minutes  (?).  Explain  the  action  of  the  chlorine  water. 

The  silver  nitrate  test  will  enable  you  to  tell  whether  or 
not  a  given  compound  belongs  to  the  group  of  chlorides, 
bromides,  and  iodides.  The  test  with  chlorine  water  and 
carbon  tetrachloride  will  enable  you  to  distinguish  the  three 
members  of  the  group  from  one  another. 

71 


EXERCISE  49 


THE  PREPARATION  AND  PROPERTIES  OF  CARBON 
MONOXIDE 

Apparatus.  The  apparatus  shown  in  Fig.  44  :  A  is  a  funnel,  con- 
nected by  a  rubber  tube  with  a  piece  of  glass  tubing  which  passes 
through  a  stopper  into  the  250-cc.  flask  B ;  C  is  a  small  clamp ; 
pneumatic  trough ;  3  wide-mouthed  bottles ;  3  glass  plates  10  cm. 
square;  burner;  ring  stand.  Apparatus  shown  in  Fig. 45:  A  and  B  are 
glass  tubes  connected  by  rubber  tubing ;  C  is  a  wide-mouthed  bottle. 

Materials.  Concentrated  sulfuric  acid;  25  cc.  formic  acid  (50%); 
limewater  (R.  S.) ;  1  g.  black  copper  oxide  powder. 

PRECAUTIONS.  Carbon  monoxide  is  a  nearly  odorless  and  very  poison- 
ous (/as.  All  of  the  experiments  must  be  performed  in  the  hood.  After  the 
gas  is  generated,  pour  the  contents  of  the  generator  flask  into  a  sink  or 
jar  in  the  hood. 

a.  Eemove  the  stopper  from  the  flask  B  (Fig.  44),  pour  in 
15  cc.  of  sulfuric  acid  and  connect  the  apparatus  as  shown 
in  the  figure.  Close  the 
clamp  C  and  partially 
fill  the  funnel  A  with 
the  formic  acid.  Now 
open  the  clamp  care- 
fully so  that  the  formic 
acid  will  enter  the  flask, 
a  drop  at  a  time.  Allow 
8  or  1 0  drops  to  flow  in ; 
then  close  the  clamp. 
If  the  reaction  does  not 
begin  (as  indicated  by 
absence  of  efferves- 
cence of  the  liquid  in  the  flask  and  escape  of  gas  through 
the  exit  tube),  heat  the  flask  very  gently  until  the  reaction 
starts ;  then  open  the  clamp  again  and  admit  the  formic 

72 


FIG.  44 


acid,  a  drop  at  a  time,  so  as  to  secure  a  regular  flow  of  gas 
from  the  flask.  If  necessary,  add  more  formic  acid  to  the 
funnel  so  as  to  keep  it  partially  filled  (?).  Collect  three 
bottles  of  the  gas  as  shown  in  the  figure.  Close  the  clamp 
so  as  to  stop  further  generation  of  gas.  Slip  the  glass  plates 
over  the  mouths  of  the  bottles  and  remove  the  bottles  from 
the  trough.  In  the  first  bottle  filled,  is  the  gas  pure  car- 
bon monoxide  ?  Eemove  the  glass  cover  and  test  it  with 
a  flame  (?).  Kepeat  with  the  second  bottle  filled  (?).  Slip 
the  glass  plate  from  the  third  bottle  just  far  enough  to  pour 
into  the  bottle  5  cc.  of  clear  limewater ;  then  quickly  replace 
the  glass  plate  and,  holding 
it  firmly  against  the  mouth 

of  the  bottle,  shake  the  con-  FJ  & 

tents   of   the   bottle.    Note  [••     \ 


any  change  in  the  appear- 
ance of  the  limewater.  Now  pIG  45 
tip  the  bottle  as  far  as  pos- 
sible without  spilling  the  limewater ;  remove  the  glass  plate 
and  quickly  ignite  the  gas,  holding  the  bottle  in  this  posi- 
tion so  that  at  least  a  portion  of  the  combustion  product 
may  be  retained  in  the  bottle.    When  the  flame  dies  out,  at 
once  cover  the  mouth  of  the  bottle  with  the  glass  plate  and 
shake  the  contents.    Note  the  results. 

b.  Introduce  into  the  tube  A,  Fig.  45,  a  small  amount  of 
copper  oxide  and  arrange  the  apparatus  as  shown  in  the 
figure.  Now  connect  the  exit  tube  D  (Fig.  44)  with  the  tube 
A  (Fig.  45).  Heat  the  copper  oxide  gently ;  at  the  same 
time  pass  a  slow  current  of  carbon  monoxide  through  the 
tube,  generating  the  gas  as  under  a.  Continue  until  the 
limewater  and  copper  oxide  both  have  visibly  changed. 
Describe  the  results  and  write  the  equations  for  all  the 
reactions  involved. 


73 


EXERCISE  50 

CARBONIC  ACID  AND  ITS  SALTS  (CARBONATES) 

Apparatus.  Hydrogen  generator,  as  used  for  preparing  carbon 
dioxide  in  Exercise  19  ;  small  beaker ;  5  test  tubes. 

Materials.  Pieces  of  marble  for  generating  carbon  dioxide ;  hydro- 
chloric acid ;  blue  litmus  paper ;  5  cc.  sodium  hydroxide  solution 
diluted  with  10  cc.  water ;  1  g.  of  the  common  carbonates,  such  as 
sodium  carbonate,  magnesium  carbonate,  calcium  carbonate ;  25  cc. 
limewater  (R.S.). 

a.  Generate  carbon  dioxide  and  pass  the  gas  through  25  cc. 
of  water.    The  gas  combines  with  the  water  to  form  carbonic 
acid  (E).   Taste  the  liquid.   Is  the  acid  formed  strong  enough 
to  affect  blue  litmus  paper? 

b.  Pass  carbon  dioxide  through  a  solution  of  sodium  hy- 
droxide until  the  gas  is  no  longer  absorbed ;  then  evaporate 
the  solution  to  dryness.  Explain.   Could  a  solution  of  sodium 
hydroxide  be   used  in  place  of  a  solution  of  calcium  hy- 
droxide (limewater)  in  testing  for  carbon  dioxide? 

c.  Examine  the  physical  properties  of  such  carbonates  as 
are  available.    What  ones  are  soluble  in  water   (p.  395   of 
text)  ?    Test  the  action  of  hydrochloric  acid  or  sulfuric  acid 
on  each  by  adding  1  or  2  drops  of  the  acid  to  0.1  g.  of  the 
carbonate  on  a  watch  glass.    What  evidences  have  you  that 
a  gas  is  evolved  ?    Arrange  a  simple  apparatus  to  determine 
whether  or  not  the  gas  evolved  is  carbon  dioxide,  then  test 
one  or  more  of  the  carbonates. 

All  carbonates  when  treated  with  hydrochloric  acid  or  sul- 
furic acid  evolve  carbon  dioxide.  This  reaction  serves  as  a 
good  test  for  carbonates. 

Can  you  suggest  any  reason  why  carbon  dioxide  is  so 
readily  liberated  from  carbonates  ? 


74 


EXERCISE  51 

A  STUDY  OF  SOME  OF  THE  HYDROCARBONS 

Apparatus.  Evaporating-dish  ;  burner ;  hard-glass  tube  fitted  with 
a  cork  and  a  delivery  tube,  as  shown  in  Fig.  20  ;  two  250-cc.  bottles ; 
pneumatic  trough  ;  watch  glass  ;  beaker ;  stirring-rod ;  test  tubes. 

Materials.  15  g.  soda  lime  (mixture  of  sodium  hydroxide  and 
calcium  hydroxide)  ;  10  g.  fused  sodium  acetate ;  iron  wire ;  bit  of 
calcium  carbide  (size  of  a  bean)  ;  sulf  uric  acid ;  sodium  hydroxide  ; 
wooden  splints  ;  10  cc.  each  of  low-boiling  gasoline  and  of  kerosene  ; 
1  g.  paraffin ;  1  cc.  of  cottonseed  oil. 

*  a.  Methane.  Intimately  mix,  by  grinding  together 'in  a 
mortar,  15  g.  of  soda  lime  and  10  g.  of  fused  sodium  acetate. 
Transfer  the  mixture  to  the  hard-glass  tube  used  in  prepar- 
ing oxygen  and  proceed  just  as  in  the  preparation  of  oxygen, 
except  that  the  tube  should  be  clamped  in  a  horizontal 
position  while  being  heated.  Collect  over  water  one  or  two 
bottles  of  the  evolved  gas.  Note  the  color  and  odor  of  the 
gas.  Is  it  inflammable  ? 

Sodium  acetate  has  the  formula  NaC2H302.  When  heated 
with  the  sodium  hydroxide,  methane  is  generated  according 
to  the  following  reaction: 

NaC2H302  +  NaOH >-  Na2C03  +  CH4 

b.  Acetylene.    Nearly  fill  a  test  tube  with  water  and  drop 
into  it  a  small  piece  of  calcium  carbide.    Note  the  gas  evolved 
(R).    Ascertain  by  holding  a  lighted  splint  at  the  mouth  of 
the  tube  whether  the  gas  is  inflammable. 

c.  Obtain  from  the  instructor  a  few  drops  each  of  gasoline 
and  of  kerosene.    Test  the  inflammability  of  each  by  dipping 
the  end  of  a  glass  rod  in  the  liquid  and  then  touching  it  to 
the  tip  of  a  flame.    Place  ten  drops  of  gasoline  (PRECAU- 
TION :   keep  away  from  all  /lames)  on  a  watch  glass  (hood) 
and  set  the  glass  on  a  beaker  half  filled  with  boiling  water. 

75 


Note  the  time  required  for  its  complete  evaporation.  Repeat 
the  experiment,  using  10  drops  of  kerosene.  Which  of  the 
two  substances  is  the  more  volatile? 

d.  Pour  2  or  3   drops  of  gasoline  into  a  warm  250-cc. 
wide-mouthed  bottle.    Cork  the  bottle  and  shake  it  vigor- 
ously.   Now  remove  the  cork  and,  standing  at  arm's  length, 
bring  a  lighted  splint  to  the  mouth  of  the  bottle  (?).    What 
use  is  suggested  by  the  property  noted  in  this  experiment  ? 

e.  Compare  benzene  with  low-boiling  gasoline  (benzine) 
in  odor,  solubility  in  water  (test  by  adding  3  drops  to  5  cc. 
of  water  and  shaking),  and  inflammability.    Are  both  good 
solvents  for  fats  (test  with  3  or  4  drops  of  cottonseed  oil)? 
What  advantage  has  carbon  tetrachloride  over  benzene  and 
benzine  as  a  fat  solvent? 

/.  Study  the  properties  of  paraffin.  Is  it  soluble  in  water  ? 
in  kerosene  ?  Will  it  melt  at  the  temperature  of  boiling 
water  ?  Will  it  burn  ?  Test  the  action  of  acids  and  alkalies 
on  paraffin  by  adding  a  few  drops  of  each  to  a  bit  of  the 
paraffin  on  a  watch  glass.  What  properties  are  suggested 
by  the  term  "  paraffin  "  (see  derivation  of  word)  ? 


EXERCISE  52 
A  STUDY  OF  THE  FLAME 

Apparatus.  Burner;  wire  ga'uze ;  porcelain  dish;  glass  tube 
15  cm.  long. 

Materials.  Charcoal  (size  of  a  bean)  ;  5  cc.  limewater  (R.  S.) ; 
candle ;  wooden  splint. 

a.  Note  and  account  for  the  difference  between  the  com- 
bustion of  a  wooden  splint  and  that  of  a  piece  of  charcoal. 
What  are  the  conditions  necessary  for  the  production  of  a 
flame?  Light  a  candle  and  place  it  so  that  the  flame  is 
against  a  black  background  and  is  not  disturbed  by  air  drafts  ; 
then  note  the  different  cones  in  the  flame.  Test  the  relative 

76 


temperatures  of  different  parts  of  the  flame  by  means  of 
narrow  strips  of  splints.  Draw  a  diagram  showing  the  differ- 
ent parts  of  the  flame.  Extinguish  the  candle  flame  and  hold 
a  lighted  splint  2  or  3  cm.  from  the  wick  in  the  little  column 
of  smoke »(?). 

b.  What  two  elements  constitute  the  main  parts  of  ordi- 
nary fuels  ?    What  products  form  when  these  elements  burn 
in  air  or  oxygen  ?    Devise  simple  experiments  to  show  the 
presence  of  these   products  in  the  gases   evolved   by  the 
burning  candle. 

c.  What  is  meant  by  the  kindling  temperature  of  gases  ? 
When  a  lamp  is  first  lighted  a  film  of  liquid  often  spreads 
over  the  chimney  for  an  instant.   Ex- 
plain.    Press   a   piece   of  .wire   gauze 

halfway  down  on  a  Bunsen  flame. 
Notice  that  the  flame  does  not  extend 
above  the  gauze.  Is  this  due  to  the 
absence  there  of  combustible  gases  ? 
Test  for  their  presence  by  means  of 
a  lighted  splint.  FIG  46 

Turn  off  the  gas,  then  turn  it  on 

and  ignite  it  over  a  piece  of  wire  gauze  held  horizontally  4 
or  5  cm.  above  the  top  of  the  burner.  Note  the  results  and 
explain.  How  does  the  miner's  safety  lamp  prevent  explosions  ? 

Hold  a  porcelain  dish  in  a  small  luminous  Bunsen  flame. 
Account  for  the  deposition  of  carbon  (lampblack).  Does 
the  nonluminous  flame  deposit  carbon  ?  To  what  is  the 
luminosity  of  the  flame  due  ? 

d.  Eecall  the  experiment  on  the  Bunsen  flame  in  Exercise  2. 
That  the  center  of  the  base  of  the  Bunsen  flame  contains 

the  unburned  gas  may  be  shown  by  holding  in  it  the  end  of 
an  inclined  glass  tube  (Fig.  46)  and  igniting  the  gas  at  the 
upper  end  of  the  tube. 


77 


EXERCISE  53 
THE  SUGARS 

Apparatus.    3  test  tubes ;  2  small  beakers ;  stirring-rod ;  burner. 

Materials.  3.5  g.  copper  sulfate  crystals  dissolved  in  50  cc.  water 
(label  this  solution  "A");  17.5  g.  sodium  potassium  tartrate  (Ro- 
chelle  salts)  dissolved  in  50  cc.  sodium  hydroxide  solution  (label 
this  solution  "  B  " ;  solutions  A  and  B  should  be  poured  into  bottles 
and  reserved  for  future  exercises)  ;  5  cc.  commercial  glucose  or  Karo 
corn  sirup ;  2  g.  sucrose ;  1  g.  each  of  sweets  such  as  candy,  honey, 
molasses ;  2  or  3  g.  sodium  carbonate  dissolved  in  as  little  water  as 
possible ;  red  litmus  paper ;  hydrochloric  acid. 

a.  The  test  for  dextrose.    The  most  common  test  for  dex- 
trose is  the  reaction  with  Fehling's  solution.    This  is  pre- 
pared as  needed  by  mixing  equal  volumes  of  solutions  A  and 
B,  prepared  as  directed  above. 

Pour  into  a  test  tube  about  3  cc.  each  of  solutions  A  and 
B.  When  thoroughly  mixed,  the  resulting  solution  should 
be  deep  blue,  but  perfectly  clear.  Heat  the  blue  solution 
nearly  to  boiling,  add  1  or  2  drops  of  commercial  glucose 
(Karo  corn  sirup  will  do  as  well),  and  continue  the  heating 
for  a  few  moments.  The  copper  sulfate  in  the  solution  is 
reduced  to  cuprous  oxide  by  the  dextrose,  and  this  separates 
in  the  form  of  a  red  or  yellow  solid.  Levulose  will  act  in  the 
same  way.  Dissolve  samples  of  candy,  honey,  and  molasses 
in  a  little  water  and  test  for  the  presence  of  dextrose  and 
levulose  in  these  sweets. 

b.  The  action  of  cane  sugar  on  Feliling's  solution.     In  a 
similar  way  try  the  action  of  pure  cane  sugar  on  Fehling's 
solution  (?). 

Now  dissolve  about  1  g.  of  the  sugar  in  10  cc.  of  water. 
Add  4  or  5  drops  of  concentrated  hydrochloric  acid  and 
slowly  heat  nearly  to  boiling.  Set  the  solution  aside  for  about 
five  minutes,  then  cool  and  neutralize  the  acid  present  by 

78 


adding  a  concentrated  solution  of  sodium  carbonate  until  the 
resulting  mixture  is  just  alkaline  to  litmus  paper.  Now  test 
this  with  Fehling's  solution  as  in  a.  Account  for  the  result. 

EXERCISE  54 

A  STUDY  OF  STARCH 

(Students  interested  in  the  subject  of  foods  should  perform  the  addi- 
tional exercises  included  under  Appendix  A.) 

Apparatus.  Microscope;  200-cc.  beaker;  stirring-rod;  ring  stand 
and  burner ;  3  test  tubes. 

Materials.  Iodine  solution  prepared  by  dissolving  0.5  g.  iodine 
and  2.5  g.  potassium  iodide  in  25  cc.  water  (label  this  "  Iodine  Solu- 
tion "  and  preserve  for  use  in  a  number  of  exercises) ;  0.1  g.  flour ; 
10  g.  starch ;  piece  of  bread  ;  hydrochloric  acid  ;  3  g.  sodium  carbon- 
ate dissolved  in  a  little  water ;  red  litmus  paper ;  starch  solution 
(R.  S.)  ;  Fehling's  solution. 

a.  Microscopic  appearance.  Examine  under  the  microscope 
the  appearance  of  starch  from  different  sources  (corn,  wheat) 
when  magnified.    Draw  diagrams  of  the  starch  granules. 

b.  Actions  of  acids  on  starch.    Try  the  action  of  starch 
solution  on  Fehling's  solution  (as  in  Exercise  53)  (?). 

Add  2  cc.  of  hydrochloric  acid  to  50  cc.  of  starch  solution 
in  a  beaker  and  hoil  the  contents  gently  for  thirty  minutes, 
allowing  the  solution  to  concentrate  to  about  25  cc.  Cool 
the  liquid,  neutralize  with  sodium  carbonate,  and  again  test 
the  solution  with  Fehling's  solution  (?). 

c.  Test  for  starch.    Eecall  the  action  of  iodine  on  starch 
(Exercise  47).    This  constitutes  a  good  test  for  starch. 

Test  different  foods  (such  as  bread,  potatoes,  and  corn 
meal)  for  starch.  To  do  this,  boil  from  5  to  10  g.  of  the 
food  with  100  cc.  of  water,  stirring  the  mass  thoroughly  so 
as  to  break  it  into  small  pieces ;  then  filter  it  and  cool  the 
filtrate.  Now  stir  the  filtrate  with  a  glass  rod,  the  end  of 
which  is  first  dipped  into  a  solution  of  iodine  (?). 

79 


*d.  The  action  of  heat  on  starch.  Place  3  or  4  g.  of  starch 
in  a  test  tube  and  heat  slightly  for  ten  or  fifteen  minutes, 
regulating  the  heat  so  as  not  to  burn  the  starch  (the  same 
results  may  be  obtained  by  heating  a  piece  of  bread  in  an 
oven  until  it  is  dry  and  crisp).  How  does  the  product  differ 
in  taste  from  the  original  starch  ?  The  heat  changes  a  part 
of  the  starch  into  an  isomeric  compound  known  as  dextrin. 
This  is  sweet  and  dissolves  in  water,  forming  a  mucilage- 
like  solution  which  is  used  on  the  back  of  postage  stamps 
and  for  other  similar  purposes. 

EXERCISE  55 

THE  PREPARATION  AND  PROPERTIES  OF  COMMON 
ALCOHOL  (ETHYL  ALCOHOL) 

Apparatus.  One  2000-cc.  flask  (or  bottle)  connected  with  tube 
and  bottle,  as  shown  in  Fig.  47 ;  test  tube ;  stirring-rod ;  apparatus 
shown  in  Fig.  26  ;  evaporating-dish. 

Materials.  200  g.  molasses  or  Karo  corn  sirup ;  cake  of  yeast ; 
50  cc.  limewater  (R.  S.)  ;  25  cc.  alcohol ;  15  cc.  methyl  alcohol ;  small 
amounts  ,(size  of  a  pea)  of  sugar,  starch,  salt ;  1  cc.  cottonseed  oil ; 
iodine  solution  prepared  in  Exercise  54  ;  sodium  hydroxide  solution  ; 
soda  lime  sufficient  to  fill  tube  C  (Fig.  47). 

fl.  Preparation  of  alcohol.  (It  is  suggested  that  this  exper- 
iment be  performed  by  the  instructor  or  by  students  selected 
by  the  instructor ;  after  the  alcohol  is  generated  the  liquid 
may  be  divided  among  the  different  members  of  the  class 
who  will  then  test  for  the  alcohol  as  directed  in  d.) 

Dissolve  about  200  g.  of  ordinary  molasses  in  2000  cc.  of 
water  in  the  flask  A  (Fig.  47).  Grind  a  cake  of  yeast  with 
a  little  water  and  add  it  to  the  solution  in  A.  Connect  the 
flask  as  shown  in  the  figure  (the  bottle  B  contains  lime- 
water  and  the  tube  C  contains  soda  lime).  Set  the  appara- 
tus aside  in  a  warm  place  (30°  is  best)  for  one  or  two 
days.  Note  that  a  gas  is  evolved  in  A  and  bubbles  through 

80 


the  limewater  in  B  (?).  Examine  a  drop  of  the  mixture 
in  A  under  the  microscopes  for  yeast  cells  (sjee  Fig.  136 
of  text). 

b.  Properties  of  alcohol.    Pour  a  few  drops  of  alcohol  into 
a.n  evaporating-dish,  ignite,  and  note  the  characteristics  of 
the  flame. 

Determine  whether  alcohol  is  a  good  solvent  for  (1)  sugar ; 
(2)  salt ;    (3)  starch ;    (4)   oils,  such    as   cottonseed  oil  (?). 
Does  alcohol  mix  with 
water  in  all  propor- 
tions ?    Eepeat  these 
experiments,      using 
methyl  alcohol  (?). 

c.  Test  for  alcohol. 
Pour  2  cc.  of  alcohol 
into  a  test  tube  and 
add  to  this  5  cc.  of 
iodine  solution.    Now 

add  a  solution  of  so-  FIG>  47 

dium  hydroxide,  one 

drop  at  a  time  (mix  after  the  addition  of  each  drop),  until 
the  iodine  color  vanishes ;  then  warm  gently  and  set  aside 
for  a  few  minutes.  A  yellow  precipitate  of  iodoform  (p.  302 
of  text),  of  characteristic  odor,  forms.  (If  the  amount  of 
alcohol  present  is  small,  the  iodoform  may  not  separate,  but 
its  presence  will  be  revealed  by  its  odor.) 

d.  After  the  molasses   in   experiment  a  has  fermented 
divide  the  liquid  in  A  (Fig.  47)   so  that  each  student  or 
group  of  students  will  have  from  150  to  200  cc.    Pour  the 
liquid  into  a  flask  and  distill  over  3  or  4  cc.  (Exercise  13). 
Dip  the  end  of  a  glass  rod  in  the  distillate  and  touch  it  to 
the  edge  of  a  flame  (?).    Test  the  remainder  of  the  distillate 
for  alcohol  as  in  c,  above. 


81 


EXERCISE  56 
THE  PREPARATION  OF  A  SIMPLE  ESTER 

Apparatus.    250-cc.  flask  ;  ring  stand  and  burner  ;  test  tube. 
Materials.    Acetic  acid  (R.S.);  alcohol  (R.S.);  sulfuric  acid. 

Preparation  of  ethyl  acetate.  What  is  an  ester  ?  Ethyl 
acetate  is  an  ester  derived  from  acetic  acid  by  replacing  an 
atom  of  hydrogen  in  the  acid  by  the  univalent  radical  ethyl 
(C0EL)  and  has  the  formula  C0H_  •  OH  O .  It  is  a  colorless 

\     2       o/  25232 

liquid  boiling  at  78°  and  having  a  characteristic  fragrant  odor. 
Pour  into  a  small  flask  10  cc.  of  acetic  acid  (or  of  a  satu- 
rated solution  of  sodium  acetate),  5  cc.  of  sulfuric  acid,  and 
3  cc.  of  alcohol.  Mix  well  and  heat  slightly.  Ethyl  acetate 
is  formed  and  may  be  recognized  by  its  odor.  Do  not  mis- 
take the  odor  of  the  vapor  of  alcohol  for  that  of  ethyl  acetate 
(warm  a  little  alcohol  in  a  test  tube  and  note  the  difference 
between  its  odor  and  that  of  ethyl  acetate).  The  equation 
for  the  reaction  is 

H  .  C2H302  +  C2H5OH  — >•  C2H5 .  C2H802  +  H2O 

The  sulfuric  acid  is  added  to  absorb  the  water  formed. 

This  reaction  serves  as  a  test  for  both  acetic  acid  and 
acetates. 


82 


EXERCISE  57 

PHOSPHORUS  AND  ITS  COMPOUNDS 

Apparatus.  250-cc.  wide-mouthed  bottle;  deflagrating -spoon ;  glass 
plate  ;  small  beaker ;  porcelain  crucible ;  burner. 

Materials.  0.5  cc.  phosphorus  trichloride ;  phosphorus  (size  of  a 
pea) ;  litmus  paper  (red  and  blue) ;  10  cc.  ammonium  molybdate  solu- 
tion (R. S.);  ammonium  hydroxide;  nitric  acid;  silver  nitrate  solu- 
tion (R.  S.);  2  g.  disodium  phosphate. 

a.  Pour  into  a  test  tube  about  0.5  cc.  of  phosphorus  tri- 
chloride (hood)   and  add  a  little  water,  a  drop  at  a  time. 
Mix  the  liquids  by  shaking  the  tube.  What  gas  is  evolved  (E)  ? 
Finally  add  about  5  cc.  of  water,  pour  the  liquid  into  an 
evaporating-dish,  and  evaporate  to  a  sirupy  mass.    Dilute 
this  with  a  little  water ;  transfer  the  solution  to  a  test  tube 
and  add  a  few  drops  of  a  solution  of  silver  nitrate.    Boil  the 
resulting    mixture ;    finely   divided   metallic   silver    (black) 
precipitates.     Explain. 

b.  Cover  the  bottom  of  a  wide-mouthed  bottle  (250-cc.) 
with  water  to  a  depth  of  about   1  cm.    Place  a  piece  of 
phosphorus  on  a  deflagrating-spoon  and  ignite  it  by  touching 
it  with  a  hot  wire.     Quickly  lower  the  phosphorus  into  the 
bottle  and  cover  the  mouth  of  the  bottle  with  a  glass  plate. 
When  the  phosphorus  ceases  to  burn,  withdraw  the  spoon 
and  allow  the  fumes  in  the  bottle  to  dissolve  in  the  water. 
Test  the  solution  with  litmus  paper.    What  is  present  in 
the  water  ? 

Pour  the  solution  into  a  small  beaker,  add  2  or  3  cc.  of 
nitric  acid,  and  boil  the  solution  until  about  half  of  it  evapo- 
rates. The  nitric  acid  oxidizes  to  phosphoric  acid  all  the 
phosphorus  compounds  present.  Add  a  few  drops  of  the 
solution  to  10  cc.  of  a  solution  of  ammonium  molybdate  and 
warm  gently.  Note  the  result  (the  compound  formed  has  a 

83 


very  complex  composition).  Add  ammonium  hydroxide  to 
the  mixture  until  the  liquid  is  alkaline.  Note  the  result. 
Again  acidify  the  liquid  with  nitric  acid.  Note  the  result. 
The  formation  of  a  yellow  precipitate  upon  the  addition  of 
ammonium  molybdate,  which  precipitate  is  insoluble  in  nitric 
acid  and  soluble  in  ammonium  hydroxide,  serves  as  a  good 
test  for  phosphoric  acid  and  its  salts. 

c.  Apply  a  gentle  heat  to  1  or  2  g.  of  disodium  phosphate 
placed  in  a  porcelain  crucible.  Gradually  increase  the  heat 
to  the  full  extent  and  continue  the  heating  for  about  10 
minutes.  When  cool,  dissolve  the  product  in  water  and  test 
the  solution  with  silver  nitrate  solution.  Compare  with  the 
product  obtained  by  adding  silver  nitrate  to  disodium  phos- 
phate which  has  not  been  heated.  Note  the  results.  (The 
silver  salts  of  the  acids  present  are  formed  (pp.  353,  354  of 
text).) 

EXERCISE  58 

ARSENIC  AND  SOME  OF  ITS  COMPOUNDS 

Apparatus.  Blowpipe;  piece  of  charcoal  (2  cm.  x  8cm.);  hard- 
glass  tube  (10  cm.  long  and  6  or  7  mm.  wide) ;  file ;  burner. 

Materials.  Arsenic  (size  of  a  grain  of  wheat) ;  0.1  g.  arsenious 
oxide. 

a.  Note  the  physical  properties  of  arsenic.  Place  a  bit  of 
the  arsenic  in  a  cavity  on  a  piece  of  charcoal  and  gently 
heat  it  (hood),  using  a  blowpipe.  Note  the  peculiar,  garlic- 
like  odor  (poisonous). 

&.  Introduce  into  a  hard-glass  tube  an  amount  of  arsenious 
oxide  equal  in  bulk  to  a  grain  of  wheat.  Cover  this  to  a 
depth  of  2  or  3  cm.  with  somewhat  finely  powdered  charcoal 
which  has  been  previously  heated  to  a  high  temperature  in 
a  porcelain  crucible.  See  that  the  inner  surface  of  the  tube 
above  the  charcoal  is  perfectly  clean. 

Incline  the  tube  and  heat  the  upper  portion  of  the  char- 
coal to  a  high  temperature,  then,  while  maintaining  the 

84 


charcoal  at  this  temperature,  gradually  bring  the  lower  part 
of  the  tube  also  into  the  flame.  The  upper  part  of  the  tube 
must  be  kept  as  cool  as  possible.  The  arsenious  oxide  is 
changed  into  a  vapor,  which  passes  over  the  hot  charcoal. 
Account  for  the  result  (E). 

Cut  the  tube  as  near  the  bottom  as  possible  and  remove 
the  charcoal;  then,  inclining  the  tube,  apply  a  very  gentle 
heat  to  that  portion  of  it  which  contains  the  coating.  Note 
that  small  white  crystals  are  slowly  deposited  in  the  colder 
portions  of  the  tube  (E).  Examine  these  with  a  magnifying 
glass.  Note  their  form. 

*  c.  Marsh's  test — perform  in  hood,  as  the  arsine  formed 
is  poisonous.  Arrange  an  apparatus  according  to  Fig.  22, 
substituting  for  the  tube  D  a  clean,  hard-glass  tube  about 
30  cm.  long  and  8  mm.  in  diameter,  drawn  out  to  a  jet  at 
the  end.  (Use  the  blast  lamp  in  making  the  jet.)  Generate 
hydrogen  by  the  usual  method,  and,  after  taking  the  general 
precautions,  ignite  it  as  it  escapes  from  the  glass  jet.  Suf- 
ficient acid  is  added  from  time  to  time  to  cause  a  gentle 
evolution  of  the  gas.  Now  apply  a  strong  heat  to  the  hard- 
glass  tube  at  a  place  near  its  center,  using  the  "wing- top" 
burner.  After  a  few  minutes  note  whether  any  deposit 
forms  just  beyond  the  heated  portion  of  the  tube.  If  none 
forms,  the  materials  are  free  from  arsenic.  Now  add  two 
drops  of  a  dilute  hydrochloric  acid  solution  of  arsenious 
oxide  (made  by  dissolving  a  bit  of  the  oxide  no  larger  than 
a  pinhead  in  1  cc.  of  the  dilute  acid)  to  the  generator,  rins- 
ing it  down  the  funnel  tube  with  a  little  water.  Continue 
the  heating  of  the  hard-glass  tube  at  the  same  place.  Note 
the  deposit  formed  on  the  side,s  of  the  tube.  Withdraw  the 
heat  and  hold  the  lid  of  a  porcelain  crucible  in  the  flame. 
A  black  deposit  of  arsenic  forms.  Cut  the  tube  containing 
the  deposit  so  as  just  to  remove  the  jet  and,  inclining  it,  apply 
a  gentle  heat,  as  in  b.  Account  for  the  results  and  write  the 
equations  for  all  the  reactions  involved  in  the  experiment. 

85 


EXERCISE  59 

A  STUDY  OF  SOME  OF  THE  PROPERTIES  OF 
ANTIMONY 

Apparatus.  Blowpipe;  beaker;  stirring-rod;  hydrogen  sulfide 
generator  (Fig.  42). 

Materials.  Piece  of  charcoal  (2  cm.  x  8  cm.) ;  2  pieces  of  anti- 
mony (size  of  a  grain  of  wheat);  hydrochloric  acid;  nitric  acid; 
strip  of  zinc ;  10  g.  ferrous  sulfide. 

a.  Heat  a  bit  of  antimony  on  charcoal  as  in  a,  Exercise  58. 
The  product  is  Sb2O8. 

b.  Introduce  into  a  test  tube  a  bit  of  antimony  no  larger 
than  a  grain  of  wheat  and  add  about  3  cc.  of  hydrochloric 
acid   and  then  2  or  3  drops  of  nitric  acid  (?).    After  the 
metal  has  dissolved,  pour  the  solution  into  50  cc.  of  water. 
If  a  precipitate  forms,  add  hydrochloric  acid,  drop  by  drop, 
with  constant  stirring,  until  the  precipitate  dissolves.    Half 
fill  a  test  tube  with  the  resulting  solution  and  insert  a  strip 
of  zinc.    Note  the  results  (compare  Exercise  30).    Through 
the  remainder  of  the  solution  pass  a  few  bubbles  of  hydrogen 
sulfide.    The  product  is  Sb2Sg.    Note  its  properties. 

EXERCISE  60 

A  STUDY  OF  SOME  OF  THE  PROPERTIES  OF  BISMUTH 

Apparatus.  Blowpipe;  beaker;  stirring-rod;  hydrogen  sulfide 
generator  (Fig.  42). 

Materials.  2  pieces  of  bismuth  (size  of  a  grain  of  wheat) ;  piece 
of  charcoal  (2  cm.  x  8  cm.) ;  nitric  acid ;  10  g.  ferrous  sulfide  ;  hydro- 
chloric acid. 

a.  Heat  a  piece  of  bismuth  on  charcoal,  as  in  the  case  of 
antimony  (Exercise  59).  Bi2Og  is  formed  and  is  deposited  on 
the  charcoal.  Contrast  the  effect  of  heating  arsenic,  antimony, 
and  bismuth  in  air. 

86 


b.  Eepeat  b,  Exercise  59,  substituting  bismuth  for  anti- 
mony and  using  nitric  acid  alone  as  the  solvent.  The  pre- 
cipitate formed  by  hydrogen  sulfide  is  Bi2S3.  Note  its 
properties. 

Bi(N03)3  is  formed  when  bismuth  is  dissolved  in  nitric 
acid.  Upon  pouring  this  into  water  a  reaction  takes  place 
in  accordance  with  the  following  equation : 

/OH 
Bi(N08)8  +  2  H20  — >-  Bi  ^OH  — >-  BiON03  +  H20 


The  bismuth  subnitrate  (BiON03)  is  insoluble  and  sepa- 
rates as  a  white  solid.  Upon  the  addition  of  nitric  acid,  a 
drop  at  a  time,  the  reaction  is  reversed,  Bi(N03)8  being 
formed,  which  dissolves  in  the  liquid. 

c.  Define  the  terms  hydrolysis,  basic  salt,  and  reversible 
reaction,  and  illustrate  with  examples  from  this  exercise. 

EXERCISE  61 

COMPOUNDS  OF  SILICON 

Apparatus.    Evaporating-dish  ;  ring  stand ;  burner. 
Materials.    2  cc.  water  glass  (solution  of  Na2SiO3) ;   hydrochloric 
acid. 

a.  Eecall  the  formulas  and  names  of  the  important  acids 
of  silicon. 

b.  Place  2  cc.  of  a  solution  of  water  glass  (Na2Si08)  in  an 
evaporating-dish,  dilute  with  10  cc.  of  water,  and  add  2  or 
3  cc.  of  hydrochloric  acid.    Note  the  gelatinous  precipitate 
(E).  Evaporate  to  dryness  and  heat  the  dish  gently  with  the 
bare  flame  (?).    When  cool,  add  water,  filter,  and  examine 
the  residue.   What  is  it  ? 

c.  Eecall  the  action  of  hydrofluoric  acid  on  silica  (E). 


87 


EXERCISE  62 

COMPOUNDS  OF  BORON 

Apparatus.  Platinum  wire  (piece  10  cm.  long,  fused  in  glass  tube 
for  handle  (Fig.  165,  p.  414  of  text));  burner;  beaker;  porcelain 
crucible ;  stirring-rod. 

Materials.  8  g.  borax  ;  litmus  paper  (red  and  blue)  ;  sulfuric  acid  ; 
alcohol  (R..S.) ;  1  or  2  drops  cobalt  nitrate  solution  (R;S.). 

a.  Write  the  names  and   formulas   for  three   important 
compounds  of  boron. 

b.  Make  a  little  loop  on  the  end  of  a  platinum  wire  and 
heat  it  to  redness  in  a  Bunsen  flame,  then  quickly  bring 
the  loop  in  contact  with  some  borax  and  reheat.    The  borax 
adhering  to  the  loop  will  swell  up  (owing  to  the  expulsion 
of  water  from  the  hydrate)  and  finally  form  a  clear,  glassy 
bead.    Note  the  color  imparted  to  the  flame. 

Moisten  the  bead  with  a  drop  of  sulfuric  acid  and  again 
touch  it  to  the  edge  of  the  flame.  Note  the  result  (see  c, 
below,  for  explanation).  This  serves  as  a  simple  test  for  borax. 

Moisten  the  bead  with  a  drop  of  a  solution  of  a  cobalt 
compound  and  reheat  until  the  bead  is  transparent  when 
cold.  Note  the  color  of  the  bead  now.  This  property 
serves  as  a  simple  test  for  cobalt.  (Some  of  the  other 
metals  likewise  impart  characteristic  colors  to  the  bead.) 

c.  Dissolve  5  g.  of  borax  in  15  cc.  of  boiling  water.    Test 
the  solution  with  litmus  paper.   Explain.  Carefully  add  to  the 
hot    solution  2    or   3  cc.   of  sulfuric   acid   and   stir.     Cool 
the   solution  and   filter  off   the   precipitate.    Compare   the 
precipitate  with  borax,  first,  as  to  solubility  in  alcohol,  and, 
second,  as  to  the  color  imparted  to  a  flame  when  a  small 
portion  on  a  platinum  wire  is  held  in  the  flame. 

d.  Dry  a  little  of  the  boric  acid  prepared  in  c,  transfer  to 
a  porcelain  crucible,  and  heat  until  a  clear  liquid  is  formed  (?). 

88 


EXERCISE  63 

COLLOIDS  AND  EMULSIONS 

Apparatus.  6  test  tubes  ;  2  beakers  ;  hydrogen  sulfide  generator ; 
stirring-rod  ;  tripod  and  burner. 

Materials.  0.5  g.  flowers  of  sulfur ;  alcohol  (R.  S.)  ;  1%  solution  of 
tartar-emetic  (R.S.);  ferrous  sulfide  and  hydrochloric  acid  for  pre- 
paring hydrogen  sulfide ;  ferric-chloride  solution  (R.  S.)  ;  sulf uric 
acid ;  0.5  g.  of  dried  gelatin  ;  ice  water ;  white  of  an  egg ;  nitric  acid ; 
ammonium  hydroxide;  0.5  cc.  kerosene  or  cottonseed  oil;  1%  soap 
solution  (R.S.)  ;  10  cc.  water  glass,  density  1.08  (R.S.). 

a.  Place  in  a  test  tube  a  small  amount  of  flowers  of  sul- 
fur (volume  of  a  pea).    Pour  over  this  5  cc.  of  alcohol  and 
heat  to  the  boiling  point  for  2  minutes,  so  that  a  saturated 
solution  may  be  formed.    Set  the  tube  aside  until  the  undis- 
solved  sulfur  settles  to  the  bottom  of  the  tube;  then  pour 
the  clear  supernatant  solution  into   100  cc.  of  water  and 
stir  the  liquid.    The  sulfur  separates  (?)  in  the  form  of  a 
colloid. 

b.  To  18  cc.  of  water  add  2  cc.  of  the  solution  of  tartar- 
emetic.    (So  far  as  the  experiment  is  concerned,  the  tartar- 
emetic  may  be  regarded  as  the  antimony  salt  of  tartaric 
acid;    its   real   formula   is   KSbOC4H406.)     Slowly    bubble 
hydrogen  sulfide  through  the  solution  for  2  or  3  minutes ; 
antimony  sulfide  (Sb2S3)  forms.    Does  it  precipitate  (explain)  ? 
Now  add  3  drops  of  hydrochloric  acid  to  the  liquid;  mix 
and   set  the   tube  aside   for  a  few   minutes  (?).    (See  last 
paragraph,   p.  383   of   text.)    Would  you   expect  antimony 
chloride  to   give    the   same  results   as    the  tartar-emetic  ? 
(Recall  that  tartaric  acid  is  a  weak  acid  and  hydrochloric 
acid  a  strong  one.) 

c.  Heat  100  cc.  of  water  to  boiling  and  add  3  drops  of 
the  solution  of  ferric  chloride.    Ferric  hydroxide  (Fe(OH)3) 
forms  but  remains  in  colloidal  suspension.    Now  add  2  or  3 

89 


drops  of  sulfuric  acid,  stir,  and  set  the  beaker  aside  for  a 
few  minutes.    The  ferric  hydroxide  precipitates  (?). 

d.  Place  in  a  test  tube  a  sufficient  amount  of  small  pieces 
of  dried  gelatin  to  make  a  layer  1  or  2  cm.  in  depth.    Add 
about  10  cc.  of  water  and  heat  the  water  until  the  gelatin 
forms  a  colloidal  solution  (gelatin  sol).    Now  place  the  tube 
in  ice  water  and  note  the  formation  of  a  gel.   Again  heat  and 
cool  the  substance  to  see  if  the  coagulation  of  the  gelatin  is 
a  reversible  process  (?).    Save  the  substance  for  use  under  / 

e.  Dissolve  a  small  portion  of  the  white  of  an  egg  in  10  cc. 
of  cold  water.    Divide  the  liquid  into  two  equal  parts.    Heat 
the  one  portion  to  boiling  (?).    To  the  other  portion  add  2  or 

3  drops  of  nitric  acid  (?).    Make  suitable  tests  to  determine 
whether  the  coagulation  of  the  white  of  the  egg  (albumin) 
is  a  reversible  process  (?). 

/.  To  10  cc.  of  water  glass,  density  1.08,  add  10  drops  of 
sulfuric  acid.  Mix  the  liquids  and  set  aside  until  the  next 
laboratory  period  (?). 

g.  Often  a  colloid  will  prevent  the  formation  of  a  precip- 
itate or  will  delay  crystallization ;  it  is  then  called  a  protec- 
tive colloid.  This  principle  may  be  illustrated  as  follows : 
To  20  cc.  of  water  add  4  drops  of  a  solution  of  ferric 
chloride.  Mix  thoroughly  and  half  fill  each  of  two  test 
tubes  with  the  solution.  To  the  solution  in  one  of  the 
tubes,  add  2  or  3  cc.  of  the  gelatin  sol  prepared  in  d  above, 
and  shake  the  mixture ;  then  to  each  of  the  tubes  add  3  or 

4  drops   of  ammonium  hydroxide  and  heat   the   resulting 
liquids  to  boiling.    Set  the  tubes  aside  for  a  few  minutes  (?). 

h.  Pour  0.5  cc.  of  kerosene  or  cottonseed  oil  into  each  of 
two  test  tubes.  Add  water  to  one  of  the  tubes  until  it  is 
three  fourths  filled;  to  the  other  add  an  equal  volume  of  a- 
1  %  solution  of  soap.  Close  -the  tubes  tightly  with  the 
thumbs  and  shake  the  mixtures  violently  for  1  minute: 
then  set  the  tubes  aside  and  note  from  time  to  time  the 
changes  in  the  mixtures  in  each  tube  (?). 

90 


EXERCISE  64 

GENERAL  METHODS  FOR  THE   PREPARATION  OF  THE 
COMPOUNDS  OF  THE  METALS 

Apparatus.    6  test  tubes. 

Materials.  0.1  g.  of  each  of  the  following  salts,  dissolved  in  5  cc. 
water :  (1)  calcium  chloride,  (2)  lead  nitrate,  (3)  barium  chloride, 
(4)  ferric  chloride,  (5)  silver  nitrate  (solutions  of  any  of  these  on 
the  reagent  shelf  may  be  used) ;  ammonium  carbonate  solution 
(R.  S.)  ;  0.1  g.  potassium  iodide  dissolved  in  5  cc.  water ;  hydro- 
chloric acid. 

a.  By  the  direct  union  of  the  elements.    Recall  the  forma- 
tion  of   sulfides    of   copper   and  of  iron  (Exercise  37) ;    of 
chlorides  of  copper  and  antimony  (Exercise  25).    Write  the 
equations  for  the  reactions  involved. 

b.  By  dissolving  a  metal  or  its  hydroxide  in  appropriate 
acids.    Recall  the  formation  of  zinc  sulfate  (Exercise  8) ;  of 
sodium  chloride  (Exercise  28) ;  of  copper  nitrate  (Exercise 
33).    Write  the  equations  for  the  reactions.    When  a  metal 
or  its  hydroxide  is  acted  upon  by  an  acid,  what  becomes  of 
the  metal? 

c.  By  acting  upon  a  salt  of  an  acid  with  an  acid  having 
a  higher  boiling  point.    Recall  the  action  of  sulfuric  acid 
upon   sodium  nitrate   (Exercise   33) ;   of  hydrochloric  acid 
upon  iron  sulfide  (Exercise  38);   of  sulfuric  acid  upon  flu- 
orides (Exercise  44) ;  of  sulfuric  acid  on  chlorides  (Exercise 
26) ;  of  hydrochloric  acid  on  carbonates  (Exercise  50).    Write 
the  equations  for  each  reaction  and  show  in  what  respects 
they  are  all  similar. 

d.  By  the  decomposition  of  a  compound.    Recall  the  action 
of  heat  upon  potassium  chlorate  (Exercise  7) ;  upon  copper 
nitrate  and  lead  nitrate  (Exercise  34).    Write  the  equations 
for  the  reactions  involved. 

91 


e.  The  following  compounds  are  insoluble  (see  Appendix, 
Table  of  Solubility  of  Various  Solids) :  calcium  carbonate 
(CaC08),  lead  sulfate  (PbS04),  barium  carbonate  (BaC03), 
ferric  hydroxide  (Fe(OH)3),  silver  chloride  (AgCl),  lead  iodide 
(PbI2).  Prepare  a  small  amount  of  each  in  a  test  tube  (E) 
and  state  the  general  principle  involved  in  each  reaction. 

EXERCISE  65 

THE  COMPOUNDS  OF  SODIUM 

Apparatus.  Beaker ;  hydrogen  generator  for  generating  carbon 
dioxide  (Fig.  30)  ;  250-cc.  bottle ;  hard-glass  test  tube ;  platinum 
wire  ;  burner  ;  piece  of  cobalt  glass  (10  cm.  square). 

Materials.  Litmus  paper  (red  and  blue)  ;  hydrochloric  acid ;  5  g. 
sodium  chloride  ;  5  g.  sodium  carbonate ;  sulfuric  acid  ;  2  or  3  crys- 
tals of  Glauber's  salt ;  10  g.  ammonium  carbonate  ;  marble  for  gen- 
erating carbon  dioxide  ;  3  g.  sodium  bicarbonate  ;  limewater  (R.  S.). 

a.  Kecall  experiments  with  sodium,  Exercise  27. 

b.  Dissolve  5  g.  of  sodium  chloride  in  as  little  water  as 
possible.    Set  the  solution  aside  overnight  until  some  of  the 
salt  crystallizes  out.    Examine  the  shape  of  the  crystals  (use 
magnifying  glass)  (?). 

c.  Dissolve  5  g.  of  sodium  carbonate  in  20  cc.  of  water. 
Test  the  solution  with  red  and  with  blue  litmus  paper  (?). 

Now  convert  the  sodium  carbonate  present  into  common 
salt  (R).  How  can  you  be  sure  that  the  product  contains 
no  unchanged  sodium  carbonate  ?  Describe  the  method 
(R).  Treat  some  of  the  salt  so  prepared  with  sulfuric  acid. 
What  gas  is  evolved  (R)  ? 

d.  What  changes  does  Glauber's  salt  undergo  when  exposed 
to  air  (refer  to  Exercise  43)  ? 

e.  Dissolve  10  g.  of  finely  powdered  ammonium  carbon- 
ate  in    100  cc.   of   cold   ammonium   hydroxide,  shaking   or 
stirring  the  mixture  to  secure  solution.    Saturate  this  solu- 
tion  with   sodium   chloride   by   shaking  it  with  the  finely 

92 


pulverized  salt.  Pour  off  the  clear  solution  into  a  250-cc. 
bottle  and  pass  a  slow  current  of  carbon  dioxide  through 
it  until  a  precipitate  (sodium  bicarbonate)  forms.  Filter  off 
the  precipitate,  dry  between  two  pieces  of  filter  paper,  and 
examine  (E).  If  a  precipitate  does  not  form  by  the  end  of 
the  laboratory  period,  cork  the  bottle,  and  set  it  aside  until 
the  next  laboratory  period. 

/.  Fill  a  hard-glass  test  tube  about  one-fourth  full  of 
sodium  bicarbonate  and  heat  gently.  Prove  that  carbon 
dioxide  is  evolved.  What  liquid  condenses  in  the  colder 
part  of  the  tube  ?  Write  equations  for  the  reactions  by 
which  sodium  carbonate  is  converted  into  the  bicarbonate, 
and  vice  versa. 

g.  Bend  the  end  of  a  platinum  wire  into  the  form  of  a 
small  loop  and  hold  it  in  the  Bunsen  flame  until  it  ceases  to 
give  any  color  to  the  flanfe ;  then  dip  it  into  a  solution  of  a 
compound  of  sodium  so  that  a  drop  of  the  solution  is  sus- 
pended in  the  loop ;  then  hold  it  in  the  outer  film  of  the  base 
of  a  Bunsen  flame.  Note  the  color.  Note  the  appearance  of 
the  sodium  flame  when  viewed  through  a  piece  of  cobalt  glass. 

EXERCISE  66 

*  THE  DETERMINATION  OF  THE  WEIGHT  OF  COMMON 

SALT    OBTAINED    BY    ADDING    HYDROCHLORIC    ACID 

TO    A   DEFINITE    WEIGHT    OF    SODIUM    BICARBONATE 

(QUANTITATIVE) 

Apparatus.  Evaporating-dish  and  watch-glass  cover  ;  ring  stand ; 
burner ;  balance. 

Materials.    1  g.  sodium  bicarbonate  ;  hydrochloric  acid. 

Carefully  weigh  the  evaporating-dish  and  watch  glass. 
Transfer  to  the  dish  about  1  g.  of  sodium  bicarbonate  and 
re  weigh.  Pour  4  or  5  cc.  of  water  on  the  bicarbonate,  and 
place  the  watch  glass  on  the  dish  so  that  only  the  lip  of  the 
dish  remains  uncovered.  Now  pour  down  the  lip  of  the  dish 

93 


2  or  3  drops  of  hydrochloric  acid.  Wait  until  the  efferves- 
cence caused  by  the  escape  of  the  carbon  dioxide  ceases,  then 
add  a  few  drops  more  of  the  acid.  Kepeat  until  the  addition 
of  the  acid  no  longer  causes  any  effervescence.  Now  hold  the 
watch  glass  in  the  hand  just  above  the  dish  and  with  a  little 
water  carefully  rinse  back  into  the  dish  the  liquid  which  has 
collected  on  the  undersurface  of  it.  Eemove  the  watch  glass 
and  slowly  evaporate  the  solution  (Fig.  33). 

When  the  solution  has  evaporated  nearly  to  dryness,  cover 
the  dish  with  the  watch  glass  and  heat  the  dish  with  the  tip 
of  the  flame.  Continue  the  heating  until  there  is  no  more 
liquid  left  in  the  dish  or  clinging  to  the  undersurface  of  the 
glass.  Then  withdraw  the  heat  and,  after  the  dish  is  cool, 
reweigh. 

From  your  results  calculate  the  amount  of  salt  formed 
from  1  g.  of  the  bicarbonate.  Compare  your  result  with  those 
obtained  by  other  members  of  the  class.  How  does  the  average 
of  the  results  obtained  compare  with  the  theoretical  results  ? 


EXERCISE  67 

\ 

THE  TEST  FOR  POTASSIUM;  THE  PREPARATION  OF 
POTASSIUM  NITRATE 

Apparatus.  Platinum  wire  for  flame  test;  cobalt  glass;  burner; 
small  beaker ;  stirring-rod  ;  funnel. 

Materials.  0.1  g.  potassium  nitrate  and  0.1  g.  sodium  chloride,  each 
dissolved  in  a  little  water ;  17  g.  sodium  nitrate ;  15  g.  potassium 
chloride ;  filter  paper. 

a.  Test  for  potassium.  Eepeat  g,  Exercise  65,  using  a  solu- 
tion of  a  compound  of  potassium  (?).  Note  the  appearance  of 
the  flame  through  a  piece  of  cobalt  glass  (?).  Eepeat,  using 
a  solution  containing  a  compound  of  sodium  as  well  as  one  of 
potassium.  How  could  you  detect  both  sodium  and  potassium 
if  they  were  present  in  the  same  solution  ? 

94 


*b.  Preparation  of  potassium  nitrate.  Dissolve  17  g.  of 
sodium  nitrate  in  15  cc.  of  boiling  water;  also  15  g.  of  potas- 
sium chloride  in  30  cc.  of  boiling  water.  Mix  the  two  solutions 
in  a  small  beaker  and  evaporate  (stirring  the  mixture)  to 
about  20  cc. ;  then  quickly  filter  the  hot  solution  and  set  the 
filtrate  (filtrate  A)  aside  until  cold. 

The  reaction  between  potassium  chloride  and  sodium  ni- 
trate is  reversible,  and  the  number  of  grams  of  each  of  the 
four  compounds  involved  which  dissolve  in  100  g.  of  water 
at  15°  and  100°  is  as  follows : 

15°  100°  15°  100° 

Sodium  nitrate     .     .     84     180  Potassium  nitrate     .     26     247 

Potassium  chloride  .     33       57  Sodium  chloride  .     .     36       40 

From  a  study  of  these  solubilities,  what  compound  should 
you  expect  would  separate  when  the  hot  solutions  of  sodium 
nitrate  and  potassium  chloride  are  mixed  together  ?  Test 
the  solid  on  the  filter  paper.  (Examine  the  crystals  with  a 
magnifying  glass  and  compare  with  b,  Exercise  65,  to  see 
if  your  conclusion  is  correct.  Taste  the  crystals.) 

What  solid  should  you  expect  would  separate  from  filtrate 
A  when  it  is  cooled  ?  Should  you  expect  it  to  be  pure  ? 
Examine  it  with  a  magnifying  glass.  Can  you  detect  crystals 
of  sodium  chloride  in  this  solid  ? 

Dissolve  the  solid  in  as  little  hot  water  as  possible,  cool 
the  solution,  and  again  filter  off  the  solid.  Repeat  until  no 
crystals  of  sodium  chloride  can  be  detected.  Prove  the  identity 
of  this  compound  (?). 


95 


EXERCISE  68 

THE  PROPERTIES  OF  AMMONIUM  COMPOUNDS 

Apparatus.  Evaporating-dish  and  watch-glass  cover ;  5  test  tubes; 
burner;  hydrogen  sulfide  generator  (Fig.  42). 

Materials.  Ammonium  hydroxide;  hydrochloric  acid;  sodium 
hydroxide  solution ;  litmus  paper  (red  and  blue) ;  10  g.  ferrous  sul- 
fide ;  0.2  g.  ferrous  sulf ate  dissolved  in  10  cc.  water ;  ammonium 
carbonate  (R.  S.) ;  barium  chloride  (R.  S.) ;  calcium  chloride  (R.  S.) ; 
zinc  acetate  (R.S.). 

a.  Pour  10  cc.  of  ammonium  hydroxide  into  evaporating- 
dish,  neutralize  with  hydrochloric  acid,  and  evaporate  to 
dry  ness   on  a  water  bath  (Fig.  33)  (?).    Note   the  odor  of 
the  residue. 

Introduce  about  one  half  of  the  residue  (?)  into  a  test 
tube,  add  a  few  drops  of  sodium  hydroxide  solution,  and 
heat  gently.  Note  the  odor  of  the  evolved  gas  and  its  action 
on  a  moist  strip  of  red  litmus  paper  (?).  This  reaction  serves 
as  a  good  test  for  all  ammonium  compounds. 

Cover  the  evaporating-dish  containing  the  remainder  of 
the  residue  with  a  watch  glass  and  heat  gently  with  a  small 
flame.  Note  that  the  solid  sublimes ;  that  is,  passes  directly 
from  the  solid  form  into  a  vapor  which  condenses  (partly) 
on  the  cold  surface  of  the  watch  glass. 

b.  Saturate  5  cc.  of  water  (Fig.  42)  with  hydrogen  sultide 
and  set  aside ;  also  saturate  5  cc.  of  ammonium  hydroxide 
with  the  gas  (?).    Add  a  few  drops  of  each  to  separate  por- 
tions of  ferrous  sulfate  solution  (?)  (ferrous  sulfide  is  soluble 
in  strong  acid).    In  general,  what  metals  will  be  precipitated 
by  ammonium  sulfide  and  not  by  hydrogen  sulfide  ? 

c.  Add  a  few  drops  of  ammonium  carbonate  solution  to 
solutions  of  compounds  of  each  of  the  following  elements: 
barium,  calcium,  zinc  (?). 

96 


EXERCISE  69 
DETECTION  OF  COMPOUNDS  OF  THE  ALKALI  METALS 

Recall  such  reactions  of  sodium,  potassium,  and  ammo- 
nium compounds  ;  also  of  carbonates,  sulfates,  nitrates,  sulfites, 
sulfides,  chlorides,  bromides,  iodides,  and  phosphates  as  will 
serve  to  identify  them,  and  outline  a  method  of  procedure 
in  the  identification  of  them.  Then  ask  the  instructor  for  un- 
known compounds  falling  within  this  list  and  identify  them. 

EXERCISE  70 

THE  PREPARATION  AND  PROPERTIES  OF  SOAP 

Apparatus.  Evaporating-dish ;  ring  stand  and  burner ;  large 
beaker;  stirring-rod;  funnel;  small  beaker;  4  test  tubes. 

Materials.  Alcohol  (R.S.);  5  g.  cottonseed  oil  (or  lard);  1  g. 
sodium  hydroxide  dissolved  in  2  cc.  water ;  hydrochloric  acid  ;  mag- 
nesium sulfate  (R.  S.)  ;  calcium  chloride  solution  (R.  S.)  ;  1  g.  sodium 
chloride  dissolved  in  5  cc.  water ;  litmus  paper  (red  and  blue). 

a.  Add  10  cc.  of  alcohol  to  5  g.  of  cottonseed  oil  in  an 
evaporating-dish.      To   the   resulting    mixture   add    1  g.   of 
sodium  hydroxide  dissolved  in  2  cc.  of  water.     Evaporate 
carefully  '(use  small  flame  and  do  not  let   the  tip  touch 
the  dish),  stirring  the  mixture  constantly  until  the  odor  of 
alcohol  can  no  longer  be  detected.    What  is  formed  ?    What 
remains  in  the  dish? 

b.  Add  50  cc.  of  cold  water  to  the  residue  in  the  dish, 
stir  well  for  a  few  minutes,  and  filter.     Pour  5  cc.  of  the 
filtrate  into  each  of  three  test  tubes.    To  the  first  add  2  or 
3  drops  of  hydrochloric  acid ;  to  the  second  add  a  few  drops 
of  a  solution  of  magnesium  sulfate.    In  like  manner  add  a 
few  drops  of  a  solution  of  calcium  chloride  to  the  third. 

97 


Note  what  takes  place  in  each  test  tube.  Why  do  waters 
containing  calcium  and  magnesium  compounds  (hard  waters) 
not  lather  freely  with  soap  ? 

c.  Add  a  few  drops  of  sodium  chloride  solution  to  10  cc. 
of  the  filtrate  obtained  in  b  (?)  (p.  417  of  text).    The  soap 
in  the  filtrate  prepared  in  b  is  not  in  solution  but  in  col- 
loidal suspension  (p.  383  of  text).    The  salt  causes  the  pre- 
cipitation of  the  colloid  (soap). 

d.  Recall  the  effect  of  soap  in  the  formation  of  emulsions 
(Exercise  63).    What  influence  has  this  property  upon  the 
cleansing  action  of  soap? 

EXERCISE  71 
A  STUDY  OF  SOME  OF  THE  COMPOUNDS  OF  CALCIUM 

Apparatus.  Evaporating-dish ;  ring  stand  and  burner ;  watch 
glass ;  small  beaker  ;  2  test  tubes  ;  wire  gauze  ;  glass  plate ;  platinum 
wire  for  flame  test. 

Materials.  Piece  of  lime  (size  of  a  walnut)  ;  bits  of  marble ;  hy- 
drochloric acid  ;  ammonium  carbonate  (R.  S.)  ;  ammonium  hydrox- 
ide ;  disodium  phosphate  (R.  S.)  ;  10  g.  plaster  of  Paris ;  0.1  g.  each 
of  the  chloride  or  the  nitrate  of  calcium,  strontium,  and  barium. 

a.  Immerse  a  piece  of  calcium  oxide  (lime)  as  large  as  a 
walnut  in  a  beaker  of  water  for  three  or  four  seconds.    Re- 
peat (if  necessary)  until  the  surface  of  the  lime  remains  moist 
for  ten  seconds  after  the  piece  is  withdrawn  from  the  water ; 
then  place  the  piece  on  a  watch  glass  and  set  the  watch  glass 
aside  until  the  end  of  the  period  (?).    This  is  a  convenient 
way  of  preparing  calcium  hydroxide. 

b.  Dissolve  1  or  2  g.  of  marble  in  hydrochloric  acid  (R). 
What  does  the  effervescence  indicate  ?  Evaporate  the  solution 
to  dryness  (use  the  bare  flame  and  evaporate  to  complete 
dryness  (Fig  33)).    What  is  the  composition  of  the  residue  ? 
Expose  a  small  piece  of  it  to  the  air  for  an  hour  and  account 
for  the  results. 

98 


Dissolve  the  remainder  of  the  residue  in  a  little  water  and 
divide  the  liquid  into  two  portions.  To  the  one  add  a  few 
drops  of  ammonium  carbonate  (R) ;  to  the  other  add  a  few 
drops  of  ammonium  hydroxide  and  then  of  a  solution  of 
disodium  phosphate.  The  precipitate  is  Ca3(P04)2. 

c.  Place  a  piece  of  marble  on  a  wire  gauze  and  apply  a 
strong  heat  for  about  fifteen  minutes.  When  cool,  drop  the 
residue  into  25  cc.  of  water  and  stir.  Filter,  and  test  the 
filtrate  with  litmus  paper.  Then  blow  exhaled  air  through 
the  filtrate.  Explain. 

*d.  Place  on  a  glass  plate  a  penny  which  has  been  rubbed 
with  a  drop  of  oil.  Pour  over  the  coin  a  thick  paste  prepared  by 
adding  water  to  plaster  of  Paris.  Set  the  glass  plate  aside  until 
the  paste  hardens,  then  remove  the  coin  and  note 'the  result. 

e.  Try  the  flame  tests  for  compounds  of  calcium,  of  stron- 
tium, and  of  barium  (use  the  chloride  or  nitrate),  as  in  g, 
Exercise  65,  and  note  the  results. 

EXERCISE  72 

HARD  WATERS  AND  METHODS  FOR  SOFTENING  THEM 

Apparatus.  60-cc.  bottle ;  carbon  dioxide  generator  (Fig.  30) ; 
ring  stand  and  burner ;  funnel ;  2  test  tubes  ;  small  beaker. 

Materials.  30  cc.  limewater  (R.  S.) ;  bit  of  soap  dissolved  in 
water ;  10  to  15  g.  of  marble ;  magnesium  sulf  ate  (R.  S.)  ;  filter 
paper  ;  1  g.  sodium  carbonate  dissolved  in  as  little  water  as  possible  ; 
hydrochloric  acid. 

a.  Bubble  carbon  dioxide  into  25  cc.  of  limewater  diluted 
with  an  equal  volume  of  water.    Note  that  a  precipitate  forms 
(E),  which  gradually  dissolves  as  more  of  the  gas  is  passed  ] 
through  (?).    Add  a  few  drops  of  a  soap  solution  to  5  cc.  of 
the  resulting  solution  and  note  the  result. 

Divide  the  remainder  of  the  solution  into  two  parts.  Grad- 
ually boil  the  one  part  and  note  the  result.  To  the  other 
part  add  a  few  drops  of  clear  limewater,  mix  intimately,  and 
note  the  results.  Explain. 

99 


b.  Shake  1  g.  of  calcium  sulfate  with  10  cc.  of  water  in  a  test 
tube  for  two  or  three  minutes ;  filter,  and  add  to  the  filtrate 
2  or  3  drops  of  a  saturated  solution  of  sodium  carbonate  (E). 

All  hard  waters  contain  more  or  less  calcium  acid  carbon- 
ate, calcium  sulfate,  calcium  chloride  ;  also  the  corresponding 
compounds  of  magnesium.  (The  methods  used  for  removing 
the  calcium  compounds  likewise  serve  for  removing  the 
magnesium  compounds.)  How  could  such  waters  be  softened 
on  a  large  scale  ?  Waters  softened  in  this  way  would 
contain  what  compounds  in  solution  ? 

c.  Test  some  hard  waters  from  wells  by  the  above  methods. 

EXERCISE  73 

*SOME  ADDITIONAL  EXPERIMENTS  WITH  SOAP 

Apparatus.  Three  250-cc.  bottles  ;  burette  or  graduated  cylinder ; 
2  test  tubes. 

Materials.  1  g.  soap  dissolved  in  100  cc.  distilled  water ;  ordinary 
reagents  ;  0.5  g.  sodium  sulfate. 

a.  The  determination  of  the  amount  of  soap  lost  by  using 
hard  water  for  washing.  Place  three  250-cc.  bottles  on  the 
desk.  Into  the  first  pour  100  cc.  of  hard  water  (preferably 
an  average  sample  of  the  water  used  in  your  town  or  city) ; 
into  the  second  pour  100  cc.  of  distilled  (or  rain)  water; 
and  into  the  third  pour  100  cc.  of  distilled  water  contain- 
ing 0.5  g.  of  sodium  sulfate  in  solution.  Now  add  to  each 
the  soap  solution,  1  cc.  at  a  time,  and  shake  the  bottle  vig- 
orously. Continue  adding  the  soap  solution  until  the  lather 
formed  persists  for  five  minutes.  Compare  the  amounts  of 
the  soap  solution  required  in  each  case  to  produce  a  per- 
manent lather  (?).  Does  the  presence  of  sodium  sulfate 
prevent  the  formation  of  the  lather  (sodium  sulfate  is  left 
in  waters  softened  by  ordinary  methods)  (p.  432  of  text)  ? 

It  will  be  interesting  to  make  at  least  a  rough  approxi- 
mation of  the  amount  of  hard  water  used  yearly  in  your 

100 


city  for  washing,  and  then;  tojdefje^mine  this: cost  of  the 
soap  lost  in  one  year  owing, to  the  use  pf  „ hard %  water. 

b.   The  analysis  of  wa&i*f3W^&>'*  J$^^  for 

detecting  the  presence  of  the  following  substances  if  pres- 
ent in  washing-powders :  (1)  sodium  carbonate ;  (2)  borax 
(b,  Exercise  62) ;  (3)  mineral  matter,  such  as  sand.  Test 
one  or  more  washing-powders  for  these  substances. 


EXERCISE  74 

THE  PREPARATION  AND  PROPERTIES  OF 
BLEACHTNG-POWDER 

Apparatus.  Flask  (250-cc.)  and  two  bottles  (250-cc.)  connected 
with  glass  tubing  as  shown  in  Fig.  48 ;  200-cc.  beaker ;  stirring-rod. 

Materials.  15  g.  manganese  dioxide  ;  hydrochloric  acid  ;  25  cc.  of 
water  in  bottle  B ;  10  cc.  of  sodium  hydroxide  solution  added  to 
50  cc.  of  water  in  D ;  sufficient  calcium  hydroxide  (slaked  lime)  to 
half  fill  the  tube  C ;  strips  of  colored  calico ;  sulfuric  acid. 


FIG.  48 
101 


(Hood.)  generate  .chlo?;ii\e;  in  A  (Fig.  48).  The  gas  must 
be  evolved  slowly,  for  which  rea.^n  only  a  very  gentle  heat 
is  applied  to  the  flask.,  ,The  .gas.  bubbles  through  the  water 
in  B,  then  passes  over  the  calcium  hydroxide  in  (7,  any 
unabsorbed  gas  being  caught  in  D  (?). 

When  all  of  the  chlorine  has  passed  over  from  A,  discon- 
nect the  apparatus  and  transfer  the  contents  of  the  tube  C 
to  a  beaker  and  pour  over  it  75  cc.  of  water  containing  1  cc. 
of  sulfuric  acid.  Stir  well  and  immerse  in  the  mixture 
some  strips  of  colored  calico  for  a  few  minutes  (?).  Com- 
plete the  following  equations: 

Ca(OH)2+Cl2  -  >• 
CaOCl 


EXERCISE  75 

MAGNESIUM  AND  ITS  COMPOUNDS 

Apparatus.  Porcelain  crucible  and  cover  ;  ring  stand  and  burner  ; 
pipe-stem  triangle  ;  evaporating-dish  ;  2  test  tubes. 

Materials.  Strips  of  magnesium  5  cm.  long  ;  small  beaker  ;  red 
litmus  paper  ;  2  to  3  g.  magnesium  carbonate  ;  magnesium  sulf  ate 
solution  (R.  S.)  ;  ammonium  chloride  (R.  S.)  ;  disodium  phosphate 
(R.  S.). 

a.  Wind  a  strip  of  magnesium  wire  into  a  coil  and  place 
it  in  a  porcelain  crucible.    Put  the  cover  on  the  crucible 
and  apply  a  gentle  heat.   Raise  the  cover  slightly  from  time 
to  time  so  as  to  admit  air.    Continue  until  the  magnesium 
is  entirely  burned,  leaving  a  white  powder.    Cool,  add  water, 
and  stir  thoroughly  ;  then  test  with  litmus  (?). 

b.  Convert   2  or  3  g.   of  magnesium   carbonate  into  the 
chloride  (R).    Evaporate  the  solution  to  complete  dryness  in 
an  evaporating-dish,  heating  the  residue  with  the  bare  flame. 
When  it  is  cool,  add  a  few  drops  of  water,  stir,  and  test 
with  litmus  (?).   Are  waters  containing  magnesium  chloride 
objectionable  for  use  in  steam  boilers  ? 

102 


c.  Pour  3  cc.  of  a  solution  of  magnesium  sulfate  into  a  test 
tube  and  add  an  equal  volume  of  a  solution  of  ammonium 
chloride.  Now  add  to  this  a  few  drops  of  a  solution  of 
disodium  phosphate  (Na2HP04).  The  precipitate  has  the 
composition  MgNH4P04.  What  is  the  name  of  this  com- 
pound ?  To  what  class  of  compounds  does  it  belong  ?  The 
above  reaction  serves  as  a  good  test  for  magnesium  compound. 

EXERCISE  76 

ZINC  AND  ITS  COMPOUNDS 

Apparatus.   Blowpipe  ;  burner ;  3  test  tubes  ;  beaker. 

Materials.  0.5  g.  zinc  ;  sulf  uric  acid  ;  sodium  hydroxide  solution ; 
ammonium  sulfide  (R.  S.)  ;  0.2  g.  sodium  carbonate  dissolved  in  3  cc. 
of  water ;  2  g.  zinc  sulfate ;  hydrochloric  acid ;  pieces  of  charcoal. 

a.  Place  a  bit  of  zinc  on  charcoal  and  heat  it  in  the  tip 
of  the  flame  of  a  blowpipe  (E).  The  resulting  compound  is 
deposited  as  a  film  on  the  charcoal.  Note  the  color  of  it. 
Is  its  color  the  same  when  hot  as  when  cold  ? 

&.  Dissolve  0.5  g.  of  zinc  sulfate  in  20  cc.  of  water.  Divide 
this  solution  into  3  parts  and  test  with  the  following  reagents : 
(1)  sodium  hydroxide  solution  (1  drop,  or  just  sufficient  to 
cause  a  precipitate) ;  zinc  hydroxide  precipitates  (E),  but  the 
precipitate  dissolves  again  if  an  excess  of  sodium  hydroxide 
is  added;  (2)  ammonium  sulfide  (E)  (note  the  color  of  the 
precipitate) ;  zinc  is  the  only  metal  which  forms  an  insoluble 
white  sulfide ;  (3)  sodium  carbonate  solution ;  a  basic  car- 
bonate is  formed. 

c.  Devise  a  process  for  converting  zinc  sulfate  into  zinc 
chloride.  Submit  the  process  to  your  instructor  for  approval. 
When  approved,  prepare  some  of  the  chloride  according  to 
your  process.  For  what  is  the  compound  used  ? 


108 


EXERCISE  77 

ALUMINIUM  AND  ITS  COMPOUNDS 

Apparatus.  5  test  tubes ;  blowpipe  ;  burner ;  2  beakers ;  piece  of 
charcoal. 

Materials.  1  g.  aluminium  ;  hydrochloric  acid  ;  ammonium  hydrox- 
ide ;  sodium  hydroxide ;  aluminium  sulf  ate  solution  (R.  S.)  ;  2  or 
3  drops  of  cobalt  nitrate  solution  (R.  S.) ;  1  g.  sodium  carbonate 
in  5  cc.  of  water ;  aluminium  sulf  ate  and  potassium  sulf  ate  sufficient 
to  make  20  g.  of  crystals  of  potassium  alum. 

a.  Note  the  physical  properties  of  aluminium.    Add  5  cc. 
of  water  to  a  bit  of  the  metal  in  a  test  tube  and  add  hydro- 
chloric acid,  a   drop  at  a  time,  sufficient  to   dissolve  the 
metal.    Filter  (if  necessary)  and  dilute  the  solution  to  about 
10  cc.  and  divide  it  into  two  equal  parts.    To  the  first  add 
ammonium  hydroxide  until  the  solution  reacts  alkaline  (E) ; 
to  the   second   add   sodium  hydroxide,  a  drop  at  a  time, 
until  a  precipitate  forms  (E).    Shake  the  latter  tube  and 
divide  the  mixture  into  two  equal  portions.    To  the  one  add 
hydrochloric  acid,  noting  the  result  (E) ;  to  the  other  add 
sodium  hydroxide  solution  until  the  precipitate  dissolves  (E). 
Is  aluminium  hydroxide  an  acid  or  a  base  ? 

b.  Prepare  some  aluminium  hydroxide  by  adding  ammo- 
nium hydroxide   to  a  solution  of  aluminium  sulfate,  and 
heat  it  on  charcoal  in  the  blowpipe  flame  (E).    Moisten  the 
residue  with  a  drop  or  two  of  a  solution  of  cobalt  nitrate 
and  reheat.    Note  the  result.    Advantage  is  taken  of  this 
property  in  detecting  the  presence  of  aluminium. 

c.  Add  a  solution  of  sodium  carbonate  to  a  solution  of 
any   salt   of   aluminium.    Note   that  a   gas   is  evolved  (?). 
Devise  a  method  for  determining  whether  or  not  this  gas 
is  carbon  dioxide,  and  make  the  test. 

d.  Calculate  the  weights  of  aluminium  sulfate  (the  crystals 
of  aluminium  sulfate  have  the  formula  A12(S04)3  -  18H20) 

104 


and  of  potassium  sulfate  required  to  prepare  20  g.  of  crystals 
of  potassium  alum ;  then  dissolve  these  amounts  of  the 
two  compounds  separately  in  as  little  water  as  possible, 
mix  the  two  solutions  thoroughly,  and  set  aside  for  a  few 
days  to  crystallize.  If  a  string  is  suspended  in  the  liquid, 
the  crystals  will  deposit  on  it.  These  may  then  be  withdrawn 
and  their  properties  studied  (?). 

EXERCISE  78 

THE  USE  OF  ALUMINIUM  SULFATE  IN  THE  PURIFI- 
CATION OF  WATER 

Apparatus.    Three  250-cc.  wide-mouthed  bottles  ;  graduated  tube. 
Materials.    Aluminium  sulfate  solution  (R.  S.)  ;  limewater  (R.  S.). 

Label  the  three  bottles  A,  B,  and  C  respectively.  Nearly 
fill  A  and  B  with  muddy  water,  pouring  a  like  volume 
of  distilled  water  into  C.  Add  5  drops  of  aluminium  sulfate 
solution  to  A  and  C  respectively.  Mix  the  contents  of  each 
bottle  thoroughly.  Now  to  bottles  A  and  C  (each)  add  10  cc. 
of  limewater.  Set  the  bottles  aside  and  examine  at  the 
beginning  of  the  next  laboratory  period  (?). 

For  experiments  on  the  use  of  aluminium  compounds  as 
mordants  in  dyeing,  see  Exercise  99,  Appendix  A. 

EXERCISE  79 

REACTIONS  OF  BAKING-POWDERS 

Apparatus.    Large  test  tube,  and  cork  to  fit ;  stirring-rod. 
Materials.     4  g.   sodium  bicarbonate;    limewater   (R.S.);    alum; 
cream  of  tartar. 

a.  Grind  together  2  g.  of  sodium  bicarbonate  and  suffi- 
cient (?)  alum  to  react  with  the  bicarbonate.  Put  the  mixture 
into  a  large  test  tube  and  cover  the  mixture  with  water. 
Cork  the  tube  tightly  and  shake  the  mixture.  Dip  a  glass 

105 


rod  into  limewater  and  remove  it  gently  so  that  a  drop  of 
the  clear  liquid  clings  to  the  end  of  the  rod ;  then  quickly 
remove  the  cork  from  the  test  tube  and  lower  the  end  of 
the  rod  into  the  tube  (?).  Write  all  reactions  involved. 

b.  Repeat  a,  substituting  cream  of  tartar  for  the  alum  (?). 

c.  What  compounds  remain  in  food  as  a  result  of  the  use  of 
an  alum  baking-powder  ?  of  a  cream  of  tartar  baking-powder  ? 
For  methods  of  analysis  of  baking-powders,  see  Exercise  98, 
Appendix  A. 

EXERCISE  80 

A  STUDY  OF  IRON,  COBALT,  AND  NICKEL 

Apparatus.  2  beakers  ;  watch  glass  ;  funnel;  flask  (250-cc.);  8  test 
tubes ;  ring  stand  and  burner. 

Materials.  Piece  of  watch  spring,  10  to  15  cm.  in  length ;  5  g.  of 
small  tacks  or  fine  iron  wire ;  0.5  g.  powdered  iron ;  filter  paper ; 
hydrochloric  acid ;  sulf  uric  acid ;  nitric  acid ;  ammonium  hydroxide  ; 
potassium  ferrocyanide  (R.  S.) ;  potassium  f erricyanide  (R.  S.) ;  potas- 
sium sulfocyanide  (R.  S.) ;  0.5  g.  cobalt  nitrate  dissolved  in  10  cc.  of 
water :  0.5  g.  nickel  nitrate  dissolved  in  10  cc.  of  water. 

a.  Heat  a  piece  of  watch  spring  (from  10  to  15  cm.  in 
length)   to  a  white  heat  in  a  Bunsen  flame.     Let  it  cool 
slowly,  and  when  cold  bend  it  to  determine  if  it  is  brittle 
(?).    Again  heat  smd^at  once  plunge  into  a  beaker  of  cold 
water.    Bend  the  piece  as  before  (?).    Reheat  the  piece,  allow 
it  to  cool  slowly,  and  again  examine  it  (?). 

b.  Place  5  g.  of  fine  iron  wire  or  small  tacks  in  a  beaker 
and  pour  over  it  15  cc.  of  water.    Now  add  4  cc.  of  concen- 
trated  sulfuric   acid  and  heat   very   gently  (hood)  until  a 
vigorous  evolution  of  gas   takes  place  (R),  then  cover  the 
beaker  with  a  watch  glass  and  set  it  aside  in  the  hood  until 
near  the  end  of  the  laboratory  period.    Then  add  10  cc.  of 
water  and  heat  slowly  until  the  liquid   boils,  stirring  the 
mixture  constantly.   Filter  off  any  undissolved  solids,  collect- 
ing the  filtrate  in  a  beaker.    Set  the  filtrate  in  your  desk 
until  the  next  laboratory  period;  then  examine  the  crystals  (?). 

106 


c.  Place  about  0.5  g.  of  iron  powder  in  a  small  flask,  pour 
over  it  5  cc.  of  water,  and  then  from  1  to  2  cc.  of  hydro- 
chloric acid.  Mix  the  contents  of  the  flask,  heat  the  flask 
slightly,  and  set  aside  in  the  hood  for  five  minutes  (?).  Add 
50  cc.  of  water,  mix  well,  and  filter.  Divide  the  filtrate  into 
two  equal  parts.  Mark  one  of  these  A  and  set  it  aside.  Add 
to  the  other  portion  about  1  cc.  of  hydrochloric  acid  and 
heat  it  nearly  to  boiling ;  then  withdraw  the  flame  and  add 
nitric  acid  (about  2  cc.  of  the  concentrated  acid  will  be  re- 
quired), a  drop  at  a  time,  with  constant  stirring,  until  the 
solution,  which  is  at  first  dark  brown,  becomes  light  yellow 
in  color  (?).  Cool  the  resulting  solution.  Call  this  solution 
B.  How  do  solutions  A  and  B  differ  in  composition  ?  Now 
compare  the  action  of  the  following  reagents  upon  solutions 
A  and  B  (add  2  or  3  drops  of  the  reagents  to  5  cc.  of  the 
solutions  in  test  tubes):  ammonium  hydroxide,  potassium 
ferrocyanide,  potassium  ferricyanide,  potassium  sulfocyanide 
(KCNS).  Tabulate  your  results  as  follows : 


FERROUS  CHLORIDE 
(Solution  A) 

FERRIC  CHLORIDE 

(Solution  B) 

Ammonium  hydroxide      .     . 
Potassium  ferrocyanide    .     . 
Potassium  ferricyanide     .     . 
Potassium  sulfocyanide    .     . 

d.  Test  separate  solutions  of  a  salt  of  cobalt  and  nickel 
with  a  borax  bead  (&,  Exercise  62) ;  with  a  solution  of  sodium 
hydroxide;  with  ammonium  sulfide.    Note  the  results. 

e.  Write  on  a  piece  of  paper,  using  the  cobalt  nitrate  solu- 
tion as  ink.    Now  heat  the  paper  gently  over  a  flame  (?) 
(invisible  ink) ;  moisten  the  paper  with  a  damp  cloth  (?). 


107 


EXERCISE  81 

A  STUDY  OF  COPPER  AND  ITS  COMPOUNDS 

Apparatus.    3  test  tubes ;  beaker ;  ring  stand  and  burner. 

Materials.  Nail ;  copper  sulf ate  solution  (R.  S.) ;  sodium  hydrox- 
ide; ammonium  sulfide  (R.  S.) ;  ammonium  hydroxide  ;  10  cm.  copper 
wire ;  hydrochloric  acid. 

a.  Eecall  the  action  of  nitric  acid  and  of  sulfuric  acid  on 
copper  (Exercises  33,  40);  also  the  action  of  chlorine  and 
sulfur  on  copper  (Exercises  25,  37).  Place  a  nail  in  a  solu- 
tion of  copper  sulfate.  Account  for  the  result. 

&.  To  a  cold  solution  of  copper  sulfate  add  one  half  its 
volume  of  sodium  hydroxide  solution.  Copper  hydroxide 
(Cu(OH)2)  is  precipitated.  Now  heat  to  boiling.  The  hydrox- 
ide is  decomposed  into  water  and  cupric  oxide  (black). 

c.  Try  the  action  of  ammonium  sulfide  on  copper  sulfate  (R). 

d.  Add  1  drop  of  ammonium  hydroxide  to  a  dilute  solu- 
tion of  copper  sulfate ;  now  continue  to  add  the  ammonium 
hydroxide,  drop  by  drop,  until  the  precipitate  which  is  at 
first  formed  is  dissolved.   How  does  th#  color  of  this  solution 
compare  with  that  of  the  original  solution  ?  This  reaction  is 
characteristic  of  copper  compounds. 

e.  Recall  the  formation  of  cuprous  oxide  (Exercise  53). 
/.  Moisten  the  end  of  a  copper  wire  with  hydrochloric 

acid  and  hold  it  in  the  edge  of  a  Bunsen  flame  (?). 


108 


EXERCISE  82 

A  STUDY  OF  MERCURY  AND  ITS  COMPOUNDS 

Apparatus.    100-cc.  beaker ;  2  test  tubes. 

Materials.  Globule  of  mercury  (size  of  a  grain  of  wheat) ;  nitric 
acid ;  copper  penny ;  0.5  g.  mercuric  oxide ;  3  cc.  solution  of  mer- 
curous  nitrate  (R.  S.) ;  hydrochloric  acid. 

a.  Note  the  physical  properties  of  mercury.  Place  a  globule 
of  it  in  a  small  beaker  and  add  (hood)  just  enough  nitric 
acid  to  dissolve  it.    Dilute  the  product  with  10  cc.  of  water 
and   place  a   copper  penny  in  the  solution.    After  a  few 
minutes  remove  the  coin  and  polish  it  with  a  piece  of  cloth. 
Account  for  the  result. 

b.  For  what  purpose  have  we  used  mercuric  oxide  ?   Place 
0.2  g.  of  it  in  a  test  tube  and  dissolve  it  in  as  little  nitric  acid 
as  possible  (R).  Then  add  water  until  the  test  tube  is  one- fourth 
full.  Into  a  second  test  tube  pour  a  similar  volume  of  a  solution 
of  mercurous  nitrate.    Now  add  2  or  3  drops  of  hydrochloric 
acid  to  each  test  tube  (R).   What  conclusions  do  you  draw  in 
reference  to  the  solubility  of  the  two  chlorides  of  mercury  ? 

c.  Prepare  some  mercuric  sulfide  (?). 

EXERCISE  83 

A  STUDY  OF  SILVER  AND  ITS  COMPOUNDS 

Apparatus.  200-cc.  beaker ;  funnel ;  blowpipe ;  4  test  tubes ; 
burner;  ring  stand. 

Materials.  Piece  of  cotton  cloth  2  or  3  cm.  square ;  silver  dime ; 
nitric  acid;  hydrochloric  acid;  ammonium  hydroxide;  filter  paper; 
hot  water ;  2  or  3  g.  sodium  carbonate ;  piece  of  charcoal ;  10  cc. 
silver  nitrate  solution  (R.S.);  solutions  of  potassium  bromide  and 
of  potassium  iodide  (R.  S.)  ;  1  cc.  formaldehyde  solution. 

a.  Place  a  drop  of  silver  nitrate  solution  on  a  piece  of 
cotton  cloth  and  warm  gently.  Can  you  wash  the  stain  away  ? 

109 


What  is  it  ?  Try  ammonia  water.  Owing  to  the  permanence 
of  this  stain,  silver  nitrate  is  sometimes  used  in  making 
indelible  ink. 

b.  Place  a  silver  dime  in  a  small  beaker  and  add  (hood) 
sufficient  nitric  acid  to  dissolve  it.     The  solution  may  be 
hastened  by  applying  a  gentle  heat.    When  the  solution  is 
complete,  dilute  the  product  with  about    25  cc.  of  water. 
Account  for  the  color  of  the  liquid.    Now  add  a  solution  of 
hydrochloric   acid   until  a  precipitate  ceases  to  form.     On 
being  stirred,  the  precipitate  (?)  settles  to  the  bottom  of  the 
beaker.    Carefully  decant  the  clear  supernatant  liquid  and 
add  ammonium  hydroxide  until  the  solution  becomes  alka- 
line (?)  (d,  Exercise  81).    Wash  the  precipitate  two  or  three 
times  by  pouring  hot  water  over  it  and  decanting.    Finally, 
remove  any  remaining  water  by  filtration.    Mix  the  product 
with  an  equal  bulk  of  sodium  carbonate,  transfer  to  a  small 
cavity  in  a  piece  of  charcoal,  and  heat  it  with  a  blowpipe. 
The    silver   salt    is    gradually   reduced   to    metallic    silver, 
which  will  fuse  into  a  globule  if  sufficient  heat  is  applied. 
How  does  this  differ  in  composition  from  the  metal  consti- 
tuting the  silver  dime  ? 

c.  Prepare  small  amounts  of   the  chloride,  the  bromide, 
and  the  iodide  of   silver  (K).    Expose  to  the  sunlight  the 
test  tubes  containing  the  precipitates  and  note  any  changes. 
For  what  are  these  compounds  used  ? 

d.  Kecall  the  formation  of  silver  sulfide  (Exercise  39). 

e.  Thoroughly  clean  a  test  tube  by  rinsing  it  with  a  few 
drops  of  nitric  acid  and  then  with  distilled  water.     Pour 
into  the  tube  2  cc.  of  silver  nitrate  solution  and  dilute  with 
an  equal  volume  of  water.    Now  add  ammonium  hydroxide, 
a  drop  at  a  time  (shake  the  tube  after  addition  of  each  drop), 
until  the  precipitate  which  forms  at  first  redissolves,  leaving 
a  clear  liquid.    Next  add  2  drops  of  a  solution  of  formalde- 
hyde, mix  thoroughly,  and  place  the  tube  in  a  beaker  of  cold 
water.    Gradually  heat  the  water  to  boiling  (?). 

110 


EXERCISE  84 
PROPERTIES  OF  TIN  AND  ITS  COMPOUNDS 

Apparatus.  100-cc.  beaker ;  piece  of  charcoal ;  blowpipe ;  ring 
stand  and  burner. 

Materials.  2  pieces  of  tin  (size  of  a  pea)  ;  hydrochloric  acid ; 
mercuric  chloride  solution  (R.S.). 

a.  Note  the  physical  properties  of  tin  (?).   Heat  a  bit  of  it 
on  charcoal  (?). 

b.  Dissolve  a  small  piece  of  the  metal  in  hydrochloric  acid 
(E).    Cool,  dilute  with  a  little  water,  and  add  1  or  2  drops 
of  the  solution  to  3  cc.  of  mercuric  chloride  solution.    A 
white  precipitate  of  mercurous  chloride  forms  (E). 

Now  add  a  few  drops  more  of  the  stannous  chloride  solu- 
tion and  heat  the  mixture  gently.  The  mercurous  chloride 
is  reduced  to  metallic  mercury,  which  forms  a  dark-gray 
precipitate  (E). 

EXERCISE  85 

A  STUDY  OF  LEAD  AND  SOME  OF  ITS  COMPOUNDS 

Apparatus.  Ring  stand  and  burner;  blowpipe;  200-cc.  beaker; 
5  test  tubes;  100-cc.  beaker;  funnel  and  filter  paper. 

Materials.  2  g.  lead  (obtain  some  scrap  lead  from  a  plumber) ; 
piece  of  charcoal ;  nitric  acid ;  ammonium  sulfide  (R.  S.)  ;  sulf uric 
acid ;  potassium  chromate  (R.  S.) ;  hydrochloric  acid ;  strip  of  zinc  ; 
2  g.  red  lead. 

a.  Note  the  physical  properties  of  the  metal.  Heat  a  small 
bit  on  charcoal.  Is  it  easily  melted  ?  Note  the  coating 
formed  on  the  charcoal  (?). 

&.  Place  about  1  g.  of  the  metal  in  a  beaker  (hood)  and 
add  20  cc.  of  water  and  5  cc.  of  nitric  acid.  Heat  gently 
until  the  metal  is  dissolved  (?).  Dilute  to  100  cc.  and  filter, 
if  necessary,  to  obtain  a  clear  solution.  Call  this  solution  A. 

Ill 


Now  test  small  portions  of  this  solution  with  ammonium 
sulfide,  sulfuric  acid,  and  potassium  chromate  (K2CrO4)  re- 
spectively (E).  Note  the  color  of  the  precipitates.  Add  a 
few  drops  of  hydrochloric  acid  to  a  test  tube  one-fourth  full 
of  solution  A.  Lead  chloride  is  -precipitated.  Heat  the  mix- 
ture to  boiling,  and  if  the  liquid  does  not  become  clear,  add 
just  enough  boiling  water  to  dissolve  the  precipitate ;  then 
set  it  aside  until  cool  and  note  the  result.  How  can  you 
distinguish  between  lead  chloride  and  silver  chloride  ? 

In  the  remainder  of  solution  A  suspend  a  piece  of  zinc  (?). 

c.  Introduce  1  g.  of  red  lead  into  a  100-cc.  beaker  and 
add  5  cc.  of  water.  Mix  well  and  add  1  cc.  of  nitric  acid. 
Stir  the  mixture  and  heat  it  gently.  Notice  the  change  in 
color  (?).  Now  add  25  cc.  of  water,  stir  the  mixture,  and 
filter.  Test  the  filtrate  for  the  presence  of  lead  (?).  Place 
the  filter  paper  and  contents  in  a  small  beaker,  add  2  or 
3  cc.  of  hydrochloric  acid,  and  stir  with  a  glass  rod  so  that 
the  acid  will  come  in  contact  with  the  solid  on  the  paper. 
Heat  the  beaker  gently.  What  gas  is  evolved  (color  and  odor)  ? 

EXERCISE  86 

*  DETECTION  OF  SILVER,  LEAD,  AND  MERCURY,  WHEN 
PRESENT  IN  THE  SAME  SOLUTION 

Apparatus.  300-cc.  beaker ;  ring  stand  and  burner  ;  stirring-rod ; 
funnel. 

Materials.  Solutions  of  silver  nitrate,  lead  nitrate,  and  mercurous 
nitrate  (R.  S.);  filter  paper;  potassium  chromate  (R.  S.)  ;  sulfuric 
acid ;  ammonium  hydroxide  ;  nitric  acid ;  hot  water. 

The  detection  of  any  one  metal  becomes  more  complicated 
when  other  metals  are  present  in  the  same  solution.  As  a 
rule  it  is  necessary  so  to  treat  the  mixture  as  to  separate  the 
metals  from  each  other.  The  principle  involved  is  illustrated 
in  the  following  procedure,  the  solution  containing  the  nitrates 
of  silver,  lead,  and  mercury  (OILS}. 

112 


Prepare  a  solution  coiitaining  0.2  g.  of  each  of  the  following 
compounds :  silver  nitrate,  lead  nitrate,  and  mercurous  nitrate. 
Dilute  with  water  to  about  200  cc.  Precipitate  with  hydro- 
chloric acid  (K).  Filter  and  fill  the  paper  with  boiling  water 
three  or  four  times,  collecting  the  liquid  as  it  flows  from  the 
funnel.  This  liquid  contains  the  lead  chloride  which  has 
been  dissolved  by  the  hot  water.  Its  presence  may  be  proved 
by  testing  separate  portions  of  the  filtrate  with  solutions  of 
potassium  chromate  and  sulfuric  acid  respectively. 

To  the  residue  on  the  filter  paper  (of  what  is  it  composed  ?) 
add  2  or  3  cc.  of  ammonium  hydroxide  and  collect  the  liquid 
as  it  drops  from  the  funnel.  This  liquid  contains  the  silver 
chloride  dissolved  from  the  residue  by  the  ammonium  hydrox- 
ide. To  prove  its  presence  add  nitric  acid  to  the  liquid  until 
just  acid  to  litmus  paper.  The  silver  chloride  is  precipitated. 

What  effect  did  the  ammonium  hydroxide  have  upon  the 
color  of  the  residue  on  the  filter  paper  ?  This  change  in  color 
is  due  to  the  action  of  ammonium  hydroxide  on  the  mercurous 
chloride,  and  serves  as  a  test  for  the  presence  of  the  latter. 

Supposing  that  the  original  solution  contained  only  one 
or  two  of  the  metals  of  the  group,  how  would  the  absence  of 
the  remaining  ones  be  indicated  ? 

EXERCISE  87 

A  STUDY  OF  SOME  OF  THE  COMPOUNDS  OF 
MANGANESE 

Apparatus.    6  test  tubes. 

Materials.  0.1  to  0.2  g.  potassium  permanganate  (KMnO4)  ;  crystal 
of  ferrous  sulfate  ;  sulfuric  acid  ;  amnlonium  sulfide  (R.  S.)  ;  ammo- 
nium carbonate  (R.  S.) ;  sodium  hydroxide ;  manganese  chloride 
solution  (R.  S.). 

a.  Examine  the  physical  properties  of  potassium  perman- 
ganate (?).  Dissolve  about  0.1  g.  of  it  in  5  cc.  of  water  (?). 
Add  a  drop  of  the  solution  to  a  solution  containing  a  small 

113 


crystal  of  ferrous  sulfate  and  2  or  3  drops  of  sulfuric  acid. 
The  ferrous  sulfate  is  changed  to  ferric  sulfate,  the  oxygen 
in  the  reaction  (see  equation  below)  coming  from  the  potassium 
permanganate,  which  is  a  good  oxidizing  agent. 

2  FeS04  +  H2S04  +  O  — >-  Fe2(S04)3  +  H2O 

&.  In  potassium  permanganate  the  manganese  acts  as  an 
acid-forming  element.  It  also  acts  as  a  base-forming  element 
in  certain  compounds.  Try  the  action  of  ammonium  sulfide, 
ammonium  carbonate,  and  sodium  hydroxide,  respectively, 
on  a  solution  of  manganese  chloride  (?). 

EXERCISE  88 

A  STUDY  OF  SOME  OF  THE  COMPOUNDS  OF  CHROMIUM 

Apparatus.    6  test  tubes. 

Materials.  Solution  of  potassium  chromate  (R.  S.)  ;  lead  acetate 
solution  (R.  S.)  ;  barium  chloride  solution  (R.  S.)  ;  ammonium  sul- 
fide  (R.  S.)  ;  sodium  carbonate  solution  (R.  S.)  ;  sodium  hydroxide  ; 
0.5  g.  chromium  chloride  or  chromium  sulfate  dissolved  in  25  cc. 
of  water. 

a.  Chromates   and  dichromates.    Write   the   formula  for 
potassium  chromate ;  for  potassium  dichromate.    Is  the  chro- 
mium an  acid-forming  or  a  base-forming  element  in  these 
compounds  ?    Add  2  or  3  drops  of  sulfuric  acid  to  a  little 
potassium  chromate  solution  (?) . 

b.  Try  the  effect  of  a  solution  of  potassium  chromate  on 
a  solution  of  a  compound  of  lead  (R) ;  also  on  a  compound 
of  barium  (E). 

c.  Add  a  few  drops  of  hydrochloric  acid  to  a  little  solid 
potassium  chromate  and  explain  the   results  (R).    Repeat, 
using  potassium  dichromate  (R). 

d.  Salts  of  chromium.    Try  the  effect  of  the  following  re- 
agents on  a  solution  of  a  salt  of  chromium :  ammonium  sulfide, 
sodium  carbonate,  sodium  hydroxide.   Write  all  the  equations. 

114 


EXERCISE  89 

*BORAX-BEAD  TESTS 

Apparatus.    Platinum  wire ;  burner. 

Materials.  Borax  (R.  S.) ;  1  cc.  of  a  solution  of  a  compound  of 
each  of  the  following  metals:  nickel,  iron,  manganese,  copper. 

Recall  the  effect  of  adding  a  trace  of  cobalt  nitrate  to  a 
borax  bead  (&,  Exercise  62).  Repeat  the  experiment,  substi- 
tuting for  the  cobalt  nitrate,  salts  of  the  following  metals : 
nickel,  iron,  manganese,  copper  (?). 


115 


APPENDIX  A 

SOME  OPTIONAL  EXERCISES  OF  SPECIAL 
INTEREST  TO  STUDENTS  OF  HOME  ECONOMICS 

EXERCISE  90 
A  STUDY  OF  TEXTILE  FIBERS 

Apparatus.  4  small  beakers  or  test  tubes ;  stirring-rod ;  burner ; 
evaporating-dish  ;  2  large  beakers  ;  microscope. 

Materials.  3  strips  each  of  uncolored  cotton,  wool,  silk,  and  linen 
cloth  (3  cm.  x  15  cm.);  50  cc.  of  sodium  hydroxide  solution  ;  strip  of 
filter  paper ;  3  strips  of  filter  paper  (2  cm.  x  10  cm.) ;  ammonium 
hydroxide ;  hydrochloric  acid  ;  sulfuric  acid. 

a.  JSffect  of  heat  upon  textile  fibers.    Ignite  the  end  of  a 
strip  of  cotton  cloth  in  a  Bunsen   flame;   then   withdraw 
from  the  flame.    Note  the  odor  of  the  burning  cloth.    Does 
the  cloth  when  ignited  continue  to  burn  ? 

Repeat,  using  strips  of  wool,  silk,  and  linen.  Can  you  dis- 
tinguish in  this  way  between  vegetable  fibers  (cotton,  linen) 
and  animal  fibers  (wool,  silk)? 

b.  How  to  distinguish  between  vegetable  fibers  (cotton,  linen) 
and  animal  fibers  (wool,  silk).    Place  a  strip  of  each  kind  of 
cloth  in  small  beakers,  cover  the  cloth  with  sodium  hydroxide 
solution,  and  boil  the  liquid  for  ten  minutes,  replacing  the 
water  as  it  evaporates  (the  cloth  must  always  be  completely 
covered  with  the  liquid);  then  set  the  beakers  aside  until 
cool  (?). 

c.  How  to  distinguish  between  the  animal  fibers.    Immerse 
strips  of  silk  and  wool  in  concentrated  hydrochloric  acid  anti. 
note  the  change  after  they  have  stood  a  few  minutes  (?), 

117 


d.  How  to  distinguish  between  the  vegetable  fibers.    Immerse 
strips  of  cotton  and  linen  in  concentrated  sulfuric  acid  for 
two  minutes  (?). 

e.  Microscopic  appearance  of  textile  fibers.    Examine  the 
appearance    of  each   kind    of  fiber   under   the    microscope. 
Compare  with  the  diagrams  on  page  330  of  text. 

/.  Parchment  paper.  Pour  20  cc.  of  sulfuric  acid  slowly 
(CAUTION),  and  with  constant  stirring,  into  a  beaker  con- 
taining 10  cc.  of  water.  Pour  the  solution  into  an  evaporating- 
dish  and  allow  to  cool.  Draw  strips  of  filter  paper  slowly 
through  the  acid  and  then  immerse  them  in  a  large  beaker 
of  water.  Finally,  wash  the  strips  in  a  large  beaker  of  water 
containing  2  or  3  drops  of  ammonium  hydroxide. 

When  the  strips  are  dry,  compare  their  properties  with 
those  of  the  untreated  paper. 

EXERCISE  91 

THE  DETERMINATION  OF  THE  AMOUNT  OF  ALCOHOL 
PRESENT  IN  AN  ALCOHOLIC  LIQUID  (QUANTITATIVE) 

Apparatus.  Flask  and  condenser  connected  as  is  shown  in  Fig.  49 
(A  is  a  250-cc.  flask,  and  C  a  flask  which  holds  100  cc.  when  filled  to 
a  point  marked  on  its  neck  (a  graduated  cylinder  may  be  used  in  its 
place)) ;  ring  stand  and  burner ;  hydrometer  reading  from  0.900  to 
1.000;  cylinder. 

Materials.  100  cc.  of  any  alcoholic  liquid,  such  as  an  alcoholic 
medicine. 

The  method  commonly  used  is  based  on  the  fact  that  the 
specific  gravity  of  an  aqueous  solution  of  alcohol  varies  ac- 
cording to  the  percentage  of  alcohol  present.  Tables  have 
been  worked  out  with  great  care,  giving  the  specific  gravities 
of  solutions  of  alcohol  of  various  strengths.  If  we  know  the 
specific  gravity  of  an  aqueous  solution  of  alcohol,  therefore, 
it  is  only  necessary  to  refer  to  the  table  and  read  the  per- 
centage of  alcohol.  These  tables  are  calculated  for  certain 

118 


temperatures,  so  that  in  determining  the  specific  gravity  of 
the  alcohol  care  must  be  taken  that  the  temperature  of  the 
solution  is  the  same  as  that  indicated  in  the  tables  used. 
These  tables  are  given  in  Allyn's  "  Elementary  Applied 
Chemistry  "  (pp.  66~75);  also  in  Bulletin  107,  United  States 
Department  of  Agriculture ; 
also  in  the  "  United  States 
Pharmacopoeia  "  used  by  the 
druggist. 

Pour  exactly  100  cc.-  of 
any  alcoholic  liquid  into  a 
flask  A  (Fig.  49)  and  distill 
over  about  50  cc.,  collecting 
the  distillate  in  the  100-cc. 
flask,  as  shown  in  the  fig- 
ure. Since  alcohol  is  quite 
volatile  (boiling  point  78.3°), 
all  of  the  alcohol  present 
in  the  100  cc.  of  liquid  will 
be  contained  in  the  50  cc. 
of  the  distillate.  Now  dilute 
the  distillate  to  exactly 
100  cc.,  mix  thoroughly,  pour  into  a  cylinder,  and  having 
brought  it  to  the  proper  temperature,  determine  its  specific 
gravity  by  means  of  a  hydrometer.  Kefer  to  the  tables  for 
the  percentage  of  alcohol  present  in  the  distillate.  Why  is 
it  necessary  to  distill  the  liquid  ?  Why  dilute  the  distillate 
to  100  cc.  before  taking  the  specific  gravity  ? 


FIG.  49 


119 


EXERCISE  92 
THE  EFFECT  OF  PRESERVATIVES 

Apparatus.  Two  250-cc.  bottles  or  beakers  ;  500-cc.  beaker ;  2  test 
tubes ;  ring  staod  and  burner. 

Materials.  300  cc.  sweet  milk;  drop  of  formalin ;  10  cc.  hydrochloric 
acid  to  which  is  added  1  drop  of  a  solution  of  ferric  chloride  (R.  S.)  ; 
1  g.  sodium  benzoate. 

a.  The  effect  of  formaldehyde  on  milk.    Thoroughly  clean 
two  small  bottles  with  hot  water  and  half  fill  each  with 
sweet  milk.    Add  to  the  milk  in  one  of  the  bottles  a  drop 
of  formalin  and  mix  thoroughly.    Now  pour  about  5  cc.  of 
milk  from  each  of  the  two  bottles  into  separate  test  tubes; 
add  to  each  an  equal  volume  of  concentrated  hydrochloric 
acid  to  which  has  been  added  just  a  trace  of  ferric  chloride 
solution  (the  ordinary  commercial  hydrochloric  acid  serves 
the  purpose  well,  since  it  usually  contains  a  trace  of  ferric 
chloride  as  an  impurity). 

Mix  the  contents  of  each  of  the  tubes  thoroughly  and  set 
them  in  a  beaker  of  boiling  water.  Note  any  change  in 
color.  How  can  you  detect  the  presence  of  formaldehyde 
in  milk? 

Set  the  two  bottles  containing  the  remainder  of  the  milk 
aside  and  examine  from  time  to  time,  noting  when  the  milk 
in  each  becomes  sour. 

b.  The  effect  of  sodium  benzoate  on  sweet  cider  or  grape 
juice.    The  student  may  likewise  study  the  action  of  sodium 
benzoate  in  preventing  the  fermentation  of  sweet  cider  or 
grape  juice.    In  such  cases  the  weight  of  the  preservative 
added  to  the  beverage  should  be  from  0.1  to  0.2  per  cent  of 
the  weight  of  the  beverage. 

The  use  of  formaldehyde  in  foods  is  no  longer  permitted  by 
the  Federal  laws,  since  it  is  a  poison.  The  use  of  sodium 

120 


benzoate  is  permitted  in  certain  foods.  Do  you  see  any  reason 
why  the  Federal  law  should  prohibit  entirely  the  use  of  pre- 
servatives in  milk  but  permit  the  use  of  sodium  benzoate  in 
certain  foods,  such  as  jams  and  catchup  ? 


EXERCISE  93 

A  STUDY  OF  VINEGAR  (QUANTITATIVE) 

Apparatus.  Evaporating-dish ;  beaker ;  ring  stand  and  burner ; 
2  burettes. 

Materials.  30  cc.  each  of  different  kinds  of  vinegars ;  1  cc.  phenol- 
phthalein  solution  (R.  S.)  ;  10  cc.  sodium  hydroxide  solution  (on  desk) 
diluted  to  100  cc.  with  water ;  standard  oxalic  acid  solution  (R.  S.). 

a.  Determination  of  the  solids  in  vinegar  (quantitative). 
Weigh  a  small  evaporating-dish  and  pour  into  it  a  definite 
volume  (say  25  cc.)  of  vinegar.    Evaporate  the  vinegar  to 
complete  dryness  (Fig.  33)  and  carefully  wipe  the  bottom  of 
the  dish  with  a  dry  towel.    Weigh  it  once  more. 

From  your  results  calculate  the  amount  of  solid  matter  in 
100  cc.  of  the  vinegar.  Pure  cider  vinegar  should  contain 
not  less  than  1.6  g.  of  solids  in  100  cc.  of  vinegar  (this  is  the 
limit  fixed  by  the  Federal  government  as  well  as  by  the 
statutes  of  many  of  the  individual  states). 

Note  the  odor  and  taste  of  the  solid  matter  obtained  from 
the  vinegar.  The  solids  from  pure  cider  vinegar  should  have 
an  odor  and  taste  suggestive  of  baked  apples.  Other  kinds 
of  vinegar  may  be  tested  in  the  same  way.  The  character  of 
the  solids  varies  according  to  the  source  of  the  vinegar. 

b.  Determination  of  the  acidity  of  vinegar.     Dilute  with 
water  10  cc.  of  sodium  hydroxide  solution  to  100  cc.  and 
determine  the  exact  strength  of  this  solution  as  follows: 
Measure  out  from  a  burette  exactly  10  cc.  of  the  standard 
oxalic  acid  (C2H204  •  2  H2O)  solution,  and  add  to  it  2  or  3  drops 
of  phenolphthalein  solution.    Fill  another  burette  with  the 

121 


dilute  sodium  hydroxide  solution  and  allow  this  to  run  slowly 
into  the  oxalic  acid  solution  (see  Exercise  29)  until  the  last 
drop,  when  stirred  through  the  acid  solution,  turns  it  a  per- 
manent pink  color.  Note,  from  the  burette  reading,  the  exact 
volume  of  the  hydroxide  solution  used  in  neutralizing  the 
acid.  Now  calculate  the  strength  of  the  hydroxide  solution 
as  follows :  The  equation  for  the  reaction  is 

C2H20,  •  2  H20  +  2  NaOH  — >-  Na2C204  +  4  H20 

The  strength  of  the  oxalic  acid  solution  being  known, — namely, 
15  g.  to  1000  cc.,  —  the  strength  of  the  sodium  hydroxide 
solution  can  easily  be  calculated.  Insert  the  following  values : 

Milligrams  of  oxalic  acid  in  10  cc.  of  solution   .... 

Number  of  cubic  centimeters  of  sodium  hydroxide  solution 
required  to  neutralize  the  oxalic  acid  in  10  cc.  of  the  acid 
solution  ..;... . 

Milligrams  of  sodium  hydroxide  in  this  volume      .     .     . 

Milligrams  of  sodium  hydroxide  per  cubic  centimeter  of 
solution 

Having  determined  the  strength  of  the  sodium  hydroxide 
solution,  proceed  as  follows  to  determine  the  -acidity  of  a 
sample  of  vinegar: 

Introduce  exactly  5  cc.  of  vinegar  into  a  small  beaker  and 
dilute  with  about  50  cc.  of  water.  Add  2  drops  of  phenol- 
phthalein  and  run  in  the  solution  of  sodium  hydroxide  from 
a  burette  until  the  liquid  in  the  beaker  is  neutral,  as  in 
Exercise  29.  The  equation  for  the  reaction  is  as  follows : 

H  •  C2H302  +  NaOH Ktfa  •  C2H802  +  H20 

Knowing  the  strength  of  the  sodium  hydroxide  solution  and 
the  volume  of  this  solution  required  to  neutralize  the  acetic 
acid  in  5  cc.  of  vinegar,  it  is  easy  to  calculate  the  amount 
of  acetic  acid  present  in  the  5  cc.  of  vinegar.  The  Federal 
law  requires  that  vinegar  must  contain  not  less  than  4  g.  of 
acetic  acid  in  100  cc.  of  vinegar.  Give  results  of  different 
vinegars  tested. 

122 


EXERCISE  94 
TESTS  FOR  FATS  AND  PROTEINS 

Apparatus.  Stirring-rod ;  e vapor ating-dish ;  2  beakers  ;  ring  stand 
and  burner. 

Materials.  1  or  2  drops  of  cottonseed  oil;  1  or  2  g.  of  lard  or 
butter;  bit  of  cheese;  small  piece  of  bread;  small  portion  of 
white  of  egg ;  25  cc.  milk ;  nitric  acid ;  ammonium  hydroxide ; 
1  g.  flour. 

a.  Fats.    In  different  places  on  a  piece  of  white  paper 
rub  1  drop  of  various  fats,  such  as  cottonseed  oil,  cream, 
melted  lard,  and  butter.    Note  the  appearance  of  the  spot 
when  held  in  front  of  a  light  (?).    Heat  the  paper  slightly 
to  see  if  the  spot  will  disappear  (?).    Test  different  samples 
of  cheese  (melt  a  small  piece  and  rub  on  paper)  and  milk 
for  fats  by  this  method. 

b.  Proteins.    Place  a  small  portion  of  the  white  of  an  egg 
(protein)  in  a  test  tube  and  heat  it  by  dipping  the  tube 
into  boiling  water  (?). 

Pour  20  cc.  of  milk  into  an  evaporating-dish  and  heat 
gently.  Note  the  scum  that  collects  on  the  surface.  Kemove 
the  scum  with  a  glass  rod,  collect  other  portions  of  the  scum 
in  the  same  way,  and  save  for  further  tests. 

Transfer  a  portion  of  the  coagulated  white  of  egg  to  a 
small  beaker  and  moisten  it  with  2  or  3  drops  of  nitric 
acid  (?).  Wash  the  egg  free  from  acid  with  repeated  por- 
tions of  water,  then  moisten  it  with  ammonium  hydroxide  (?). 

In  the  same  way  test  for  the  presence  of  protein  in  the 
scum  which  separated  when  the  milk  was  heated.  Test  other 
substances  for  protein,  such  as  flour,  woolen  cloth,  a  clipping 
of  a  ringer  nail  (?).  Nitric  acid  stains  the  skin  yellow  (?). 

Burn  a  small  bit  of  different  kinds  of  protein,  such  as 
egg,  hair,  the  scum  of  milk  (?). 

123 


EXERCISE  95 

THE  COMPOSITION  OF  FLOUR 

Apparatus.  Beaker  (500-cc.)  ;  ring  stand  and  burner ;  porcelain 
crucible;  pipe-stem  triangle. 

Materials.  50  g.  flour ;  iodine  solution  prepared  in  Exercise  54 
for  testing  for  starch ;  cheesecloth  (from  12  to  15  cm.  square)  ;  car- 
bon tetrachloride  (R.S.). 

a.  Weigh  out  about   25  g.  of  flour  and  mix  with  just 
enough   water   to   form   a   stiff   dough,   working   it   in   the 
hands  until  it  becomes  smooth  and  elastic.    Place  the  dough 
on  a  piece  of  cheesecloth,  then  fold  the  cloth  about  the  dough 
and  tie  it  with  a  string  so  as  to  form  a  little  bag.  Nearly  fill 
your  largest  beaker  with  water,  immerse  the  bag  and  contents 
in  the  water,  and  repeatedly  squeeze  the  bag  between  the 
fingers.     Note  that   the  water  becomes   cloudy.     Eetain   a 
portion  of  this  cloudy  liquid  for  further  tests  (see  &,  below). 

Continue  the  washing  in  fresh  portions  of  water  until 
the  resulting  wash  water  remains  clear.  The  action  may  be 
hastened  by  working  the  dough  in  a  small  stream  of  run- 
ning water.  Test  for  protein  the  residue  remaining  in  the 
cloth  (?).  The  substance  is  known  as  gluten-,  burn  a  por- 
tion of  the  gluten  (?). 

b.  Test  separate  portions  of  the  cloudy  liquid  reserved  in 
a  for  starch  (Exercise  54)  and  for  sugar  (Exercise  53)  (?). 

c.  Fill  a  test  tube  about  one-fourth  full  of  flour,  add  car- 
bon tetrachloride  until  the  tube  is  half  filled,  and  shake  the 
contents  vigorously.    Set  the  tube  aside  until  the  flour  settles, 
then  pour  off  the  clear  liquid,  evaporate  it  (Fig.  33),  and 
test  the  residue,  if  any,  for  fat  (?). 

d.  Place  about  0.1  g.  of  flour  in  a  porcelain  crucible;  heat 
it  with  the  Bunsen  flame  (Fig.  16) ;  gradually  increase  the 
heat  until  only  a  white  residue  remains  (?). 

124 


EXERCISE  96 

SOME  EXPERIMENTS  WITH  MILK 

Apparatus.  Evaporating-dish ;  stirring-rods ;  ring  stand  and 
burner ;  2  beakers. 

Materials.  150  cc.  milk ;  acetic  acid  (R.  S.)  ;  Fehling's  solution  ; 
one-half  junket  tablet  (these  tablets  may  ordinarily  be  obtained 
from  any  druggist ;  they  may  always  be  had  at  very  little  cost  by 
addressing  Chr.  Hansen's  Laboratory,  Little  Falls,  New  York). 

a.  Determination  of  the  solids  and  the  water  in  milk.  Place 
a  short  stirring-rod  in  a  small  evaporating-dish  and  accu- 
rately weigh  the  two  together.  Introduce  about  20  cc.  of 
milk  and  again  weigh.  Now  evaporate  the  milk  to  dryness 
(Fig.  33),  occasionally  stirring  it  with  the  rod  to  break  the 
scum  (?),  which  would  otherwise  retard  evaporation.  (While 
the  evaporation  is  taking  place,  proceed  with  b.) 

When  the  residue  is  perfectly  dry,  carefully  wipe  the 
outside  of  the  dish,  cool,  and  reweigh.  From  your  results 
calculate  the  percentages  of  solids  and  water  in  the  milk. 
(Pure  milk  contains  not  less  than  12  per  cent  of  solid 
matter.  Consult  your  state  laws  as  to  the  minimum  amount 
of  solid  matter  allowed  in  milk  sold  in  the  state.) 

&.  The  separation  of  the  protein  (casein)  in  milk  by 
rennin.  Dissolve  about  one  half  of  a  so-called  "  junket " 
tablet  in  a  little  cold  water  and  add  the  solution  to  about 
100  cc.  of  sweet  milk  heated  until  just  lukewarm.  Stir  the 
solution,  then  cool  it  and  set  it  aside  until  the  renuin  con- 
tained hi  the  tablet  causes  the  separation  of  the  curd 
(casein).  Break  up  the  curd  by  stirring,  and  filter  it.  Save 
the  filtrate  for  further  tests. 

c.  TJie  separation  of  the  protein  in  milk  by  acid.  Add  1 
or  2  drops  of  acetic  acid  (vinegar  will  serve)  to  5  cc.  of 
milk,  mix  thoroughly,  and  set  aside  (?).  The  presence  of 

125 


an  acid  causes  the  casein  to  separate  (hence  the  appearance 
of  sour  milk). 

d.  The  separation  of  the  lactose  in  milk.  Evaporate  the 
filtrate  reserved  in  b,  refiltering  it  if  more  solid  matter  sepa- 
rates. Taste  the  residue  (?).  Test  it  with  Fehling's  solution 
(Exercise  53)  (?). 

EXERCISE  97 

METHODS    FOR    DISTINGUISHING    BETWEEN    BUTTER 
AND  OLEOMARGARINE 

Apparatus.  Iron  spoon ;  burner ;  wooden  splint  (match  stick  will 
do) ;  100-cc.  beaker. 

Materials.  10  g.  each  of  fresh  butter  and  oleomargarine  (also  proc- 
ess butter,  if  available)  ;  50  cc.  sweet  milk. 

a.  Foam  test.    Heat  gently  over  a  small  flame  from  2  to 
3  g.  of  the  sample  (butter  or  oleomargarine)  in  a  spoon. 
Under  these  conditions  butter  will  melt  without  sputtering 
and  with  the  formation  of  much  foam  on  the  surface,  while 
oleomargarine  will  sputter  and  give  but  little  foam.    Process, 
or  renovated,  butter  (rancid  butter  which  has  been  purified 
by  melting  the  fat,  skimming  it  off  the  surface,  and  churn- 
ing   it    with    milk    under    certain    conditions)    acts    like 
oleomargarine. 

b.  Sweet-milk  test.    Pour  50  cc.  of  sweet  milk  into  a  small 
beaker  and  heat  nearly  to  boiling.    Add  to  the  hot  milk  4 
or  5  g.  of  the  sample  and  stir  it  with  a  wooden  splint  until 
the  fat  is  melted,  then  place  the  beaker  in  ice  water  and 
continue  the  stirring  until  the  fat  solidifies.     Under  these 
conditions  butter  will  solidify  in  the  form  of  granules  which 
mix  with  the  milk.    Oleomargarine,  on  the  other  hand,  will 
collect  in  a  single  mass  so  that  it  can  be  removed  from  the 
milk  in  one  lump  with  the  wood  stirrer. 


126 


EXERCISE  98 

ANALYSIS  OF  BAKING-POWDERS 

Apparatus.  100-cc.  beaker ;  stirring-rod ;  evaporating-dish ;  ring 
stand  and  burner ;  5  test  tubes. 

Materials.  10  g.  each  of  various  kinds  of  baking-powders ;  barium 
chloride  solution  (R.  S.)  ;  sulf  uric  acid ;  nitric  acid ;  ammonium 
molybdate  solution  (R.  S.)  ;  sodium  hydroxide  solution. 

a.  Introduce  10  g.  of  a  baking-powder  into  a  beaker  and 
pour  over  it  50  cc.  of  water.     Stir  the  mixture  thoroughly 
until  no  more  gas  is  evolved,  then  filter  it,  and  test  the 
residue    and    the  .filtrate    for   the    various   ingredients,   as 
explained   below. 

b.  Starch.    Will  any  starch  present  be  in  the  residue  or 
in  the  filtrate  ?    Make  appropriate  test  (?). 

c.  Sulfates.    If  the  baking-powder  contains  alum,  the  fil- 
trate will  contain  sulfates  (?).    Make  appropriate  test  (?). 

d.  Tartrates.   Pour  5  cc.  of  the  filtrate  into  an  evaporating- 
dish,  add  5  drops  of  sulfuric  acid,  and  evaporate  to  dryness. 
Finally,  heat  the  dish  gently  with  a  bare  flame.    The  pres- 
ence of  a  tartrate  is  indicated  by  an  odor  similar  to  that  of 
burning  sugar. 

e.  Phosphates.     If  calcium  phosphate   is   present  in  the 
baking-powder,  the  filtrate  will  contain  calcium  acid  phos- 
phate.   To  detect  phosphates,  treat  5  cc.  of  the  filtrate  with 
a  few  drops  of  nitric  acid,  heat  nearly  to  boiling,  add  a  few 
drops  of   the   mixture   to    5  cc.   of   ammonium    molybdate 
solution  (?)  (compare  Exercise  57). 

/.  Ammonium  salts.  Ammonium  alum  is  sometimes  used 
in  baking-powders.  To  detect  this,  pour  5  cc.  of  the  filtrate 
into  a  test  tube,  add  an  equal  volume  of  sodium  hydroxide 
solution,  and  heat  gently.  If  ammonium  salts  are  present, 
ammonia  will  be  evolved  (?). 

127       ' 


g.  Aluminium  and  calcium.  A  baking-powder  containing 
sulfates  always  contains  aluminium,  while  one  containing 
phosphates  always  contains  calcium;  hence  the  presence  or 
absence  of  these  metals  may  be  inferred  from  the  tests  made 
for  sulfates  and  phosphates  respectively. 


EXERCISE  99 

THE  USE  OF  MORDANTS  IN  DYEING 

Apparatus.  200-cc.  beaker ;  ring  stand  and  burner ;  stirring-rod ; 
large  beaker. 

Materials.  2  strips  (2  cm.  x  6  cm.)  of  white  woolen  cloth  (nun's 
veiling  serves  well)  ;  6  strips  of  white  cotton  cloth  (cheesecloth  will 
do) ;  1  g.  sodium  carbonate  in  50  cc.  water ;  0.5  g.  tannic  acid  in 
50  cc.  water;  0.2  g.  tartar-emetic  (&,  Exercise  63)  in  50  cc.  water; 
0.1  g.  of  any  of  the  following  dyes  in  100  cc.  water  (different  students 
should  select  different  dyes  and  compare  results)  :  fuchsine,  methyl 
violet,  Bismarck  brown,  malachite  green ;  a  solution  containing 
1  g.  sodium  carbonate,  5  g.  Glauber's  salt,  and  0.1  g.  Congo  red  in 
50  cc.  water. 

a.  Most  dyes  will  dye  animal  fibers  (wool,  silk)  directly, 
but  will  dye  vegetable  fibers  (cotton,  linen)  fast  only  when 
mordants  are  used  (p.  45.8  of  text). 

Place  the  strips  of  cotton  cloth  in  a  beaker  and  cover 
them  with  the  sodium  carbonate  solution  (1  g.  in  50  cc.  of 
water)  and  boil  the  liquid  for  five  minutes.  Remove  the 
strips  and  thoroughly  rinse  them  with  water.  This  treatment 
serves  to  remove  all  foreign  matter  from  the  cloth. 

Now  completely  immerse  two  strips  of  the  cotton  cloth  in  the 
tannic-acid  solution,  heat  until  it  is  fairly  warm  to  the  hand 
(50°  or  60°),  and  maintain  the  temperature  for  ten  minutes. 
Now  remove  the  cloth  from  the  solution  and  squeeze  out 
the  liquid,  but  do  not  rinse  the  cloth ;  then  immerse  the 
strips  for  one  minute  in  the  slightly  warmed  solution  of 
tartar-emetic.  The  tannic  acid  in  the  cloth  reacts  with  the 

128 


tartar-emetic,  forming  a  salt  (known  as  antimonyl  tannate) 
which  becomes  incorporated  in  the  meshes  of  the  fiber  and 
serves  as  a  mordant.  Remove  the  cloth  from  the  solution 
and  rinse  it. 

Divide  the  solution  of  the  dye  chosen  into  three  equal  por- 
tions. Heat  one  portion  to  boiling,  immerse  a  strip  of  woolen 
cloth,  and  continue  the  heating  for  from  one  to  two  minutes  ; 
then  remove  the  cloth  and  rinse  it  thoroughly.  To  test 
whether  the  cloth  is  dyed  fast,  rinse  it  thoroughly  and  then 
wash  it  in  a  beaker  of  water  and  note  whether  the  water  be- 
comes colored  (?).  In  a  similar  way  dye  a  strip  of  unmor- 
danted  cotton  cloth  in  the  second  portion  of  the  dye  and  a 
strip  of  mordanted  cloth  in  the  third  portion,  and  determine 
in  each  case  whether  the  cloth  is  dyed  fast  (?).  Finally,  dry 
the  three  strips  of  cloth  and  insert  them  in  your  notebook. 

b.  Some  dyes  (known  as  substantive  dyes)  have  the  property 
of  dyeing  cotton  fast  without  the  use  of  mordants.  The  so- 
called  "  Diamond  Dyes  for  Cotton,"  which  may  be  purchased 
at  any  drug  store,  belong  to  this  class.  Congo  red  is  a  typical 
dye  of  this  class. 

Heat  the  solution  of  Congo  red  to  boiling,  immerse  in  it  a 
strip  of  wet  unmordanted  cotton,  and  continue  the  boiling 
for  one  or  two  minutes.  Eemove  the  cloth,  rinse,  and  test  to 
see  whether  the  cloth  is  dyed  fast.  Dry  the  strip  and  insert 
it  in  your  notebook.  (The  sodium  carbonate  and  the  sodium 
sulfate  assist  in  the  process,  but  do  not  act  as  mordants.) 

(Save  the  remaining  strips  of  cotton  for  use  in  Exercise  100.) 


129 


EXERCISE  100 

A  STUDY  OF  LAKES;   ALSO  THE  EFFECT  OF  USING 
DIFFERENT  MORDANTS  WITH  THE  SAME  DYE 

Apparatus.  Two  250-cc.  wide-mouthed  bottles ;  evaporating-dish  ; 
2  small  beakers ;  ring  stand  ;  burner ;  stirring-rods. 

Materials.  5  cc.  of  a  20%  solution  of  alizarin  paste ;  solutions  of 
aluminium  sulf ate  and  ferric  sulf ate  (R.  S.)  ;  ammonium  hydroxide  ; 
2  strips  of  cotton  cloth. 

a.  Formation  of  lakes.    Label  two  wide-mouthed  bottles 
A  and  B  respectively.    Into  each  introduce  about  10  drops 
of  the  alizarin  paste.    Next  add  to  each  of  the  bottles  2  cc. 
of  ammonium  hydroxide  and  then   200  cc.  of  water,  and 
mix  the  contents  thoroughly.   Now  add  10  cc.  of  aluminium 
sulf  ate  solution  to  bottle  A,  and  10  cc.  of  ferric  sulf  ate  to 
bottle  B,  and  set  the  bottles  aside;  note  the  appearance  of 
the   contents  at  the  end  of  the  laboratory  period,  also  at 
the  beginning  of  the  next  laboratory  period  (?).    What  is  the 
function  of  each  of  the  materials  used  ? 

b.  Mordanting  strips  of  cloth  with  aluminium  hydroxide 
and  ferric  hydroxide.    Pour  about  20  cc.  of  aluminium  sul- 
fate  solution  into  a  small  beaker  and  heat  to  boiling.    Com- 
pletely immerse  in  this  solution  one  of  the  strips  of  cotton 
cloth  prepared  in  Exercise  99,  and  continue  the  heating  for 
from  two  to  three  minutes.    Eemove  the  cloth,  squeeze  it 
between  the  fingers  to  remove  the  excess  of  the  solution, 
and  immerse  it  in  20  cc.  of  water  containing  from  1  to  2  cc. 
of  ammonium  hydroxide.    Warm  the  liquid  slightly  for  two 
minutes,  then  remove  the  cloth  and  rinse  it  twice  in  water. 
What  compound  is  now  incorporated  in  the  cloth? 

Repeat  the  operation,  using  a  solution  of  ferric  sulfate  in 
place  of  the  aluminium  sulfate.  The  resulting  strip  of  cloth 
is  mordanted  with  ferric  hydroxide. 

130 


c.  Dyeing  the  strips  of  mordanted  doth  with  alizarin. 
Pour  1  cc.  of  alizarin  paste  into  a  small  beaker,  add  20  cc. 
of  water,  stir,  and  heat  to  boiling.  Completely  immerse  one 
of  the  strips  of  mordanted  cloth  prepared  in  b  and  continue 
the  heating  and  stirring  for  three  minutes ;  then  remove  the 
cloth  and  rinse  thoroughly.  Eepeat  the  operation,  using 
the  second  strip  of  mordanted  cloth  prepared  in  b.  Dry  the 
dyed  strips  and  insert  them  in  your  notebook. 

EXERCISE  101 

THE  DETECTION  OF  DYES  IN  FOODS 

Apparatus.    Small  beaker  ;  stirring-rod  ;  ring  stand  and  burner. 
Materials.    Samples  (colored)  of  pop  and  candy;  strips  of  woolen 
cloth;  hydrochloric  acid. 

Select  different  samples  of  colored  pop.  Pour  50  cc.  of 
each  into  a  beaker,  add  2  or  3  drops  of  hydrochloric  acid, 
and  heat  to  boiling;  then  introduce  a  strip  of  woolen  cloth 
and  continue  the  heating  for  five  minutes.  Eemove  the 
cloth,  rinse,  and  note  the  color  (?). 

Samples  of  colored  candies  may  be  tested  by  first  dissolv- 
ing the  candy  in  water  and  then  testing  the  solution  for 
dyes  by  using  strips  of  woolen  cloth,  as  in  the  above  case. 

Tomato  catchup  is  sometimes  colored,  although  the  prac- 
tice is  forbidden  by  Federal  law.  To  test  a  catchup  for  dyes, 
heat  a  portion  of  the  catchup  diluted  with  water  and  im- 
merse a  strip  of  woolen  cloth  in  the  hot  mixture  for  five  min- 
utes. Eemove  the  cloth  and  rinse  thoroughly.  If  artificial 
dyes  are  present,  the  cloth  will  be  deeply  colored ;  otherwise 
it  will  have  only  a  slight  brownish  tinge  produced  by  the 
natural  coloring-matter  of  the  tomato. 


131 


EXERCISE   102 

THE  REMOVAL  OF  STAINS 

Apparatus.    4  test  tubes ;  2  beakers ;  evaporating-dish. 

Materials.  0.2  g.  tannic  acid  dissolved  in  10  cc.  water ;  ferric  sul- 
fate  (R.S.);  2  pieces  of  white  cloth  10cm.  square;  1  g.  oxalic  acid 
dissolved  in  50  cc.  water ;  hydrochloric  acid ;  2  strips  of  black  cloth 
5  cm.  square  ;  nitric  acid ;  ammonium  hydroxide  ;  a  few  drops  each 
of  cottonseed  oil  and  sirup  (molasses) ;  25  cc.  carbon  tetrachloride ; 
blotting-paper;  strips  of  cloth  stained  with  coffee  and  fruit  juice; 
Acetic  acid  (R.  S.)  ;  20  g.  bleaching-powder ;  hot  water. 

a.  Stain  two  strips  of  white  cloth  by  dipping  them  into 
a  solution  of  ferric  sulfate  until  thoroughly  saturated  and 
then  into  a  solution  of  tannic  acid  (or  they  may  be  stained 
directly  with  black  ink).    Wash  one  of  the  strips  repeatedly 
with  boiling  water  (?).    Leave  the  other  exposed  to  the  air 
until  dry;  then  try  the  effect  of  hot  water  upon  the  stain. 
If  the  stain  is  not  removed,  wash  with  a  dilute  solution  of 
oxalic  acid  and  finally  with  hot  water  (?). 

b.  Place  2  or  3  drops  of  dilute  hydrochloric  acid  upon 
a  strip  of  black  cloth  (?).    Wash  the  spots  with   10  cc.  of 
water  containing  4  or  5  drops  of  ammonium  hydroxide  (?). 
Repeat,  using  nitric  acid  in  place  of  hydrochloric  acid  (?). 

c.  Place  in  separate  test  tubes  4  or  5  drops  of  a  sirup 
and  a  like  amount  of  fat,  such  as  cottonseed  oil.    Test  the 
solubilities  of  each  in  water  and  in  carbon  tetrachloride. 
Suggest  a  method  for  removing  stains  made  by  sirups  and 
one  for  those  made  by  fats.    Stain  some  strips  of  cloth  with 
sirup  and  with  an  oil  and  test  your  methods  for  removing 
these  stains.    (In  applying  a  solvent  it  is  convenient  to  place 
the  stained  portion  of  the  cloth  over  a  piece  of  blotting- 
paper  (?).    A  small  bit  of  sponge  or  cloth,  saturated  with  the. 
solvent,  is  then  rubbed  about  the  stained  portion,  gradually 
nearing  the  stain  itself,  which  is  finally  thoroughly  rubbed.) 

13g 


Benzine  (low-boiling  gasoline)  may  be  used  in  place  of 
the  carbon  tetrachloride.  If  benzine  is  used,  however,  it  must 
be  remembered  that  it  is  very  inflammable.  Never  use  it  in 
the  vicinity  of  a  flame. 

d.  Stain  some  strips  of  cloth  with  coffee  and  with  fruit 
juices.  Are  the  stains  removed  by  washing  with  hot  water  ? 
If  the  stain  cannot  be  removed  in  this  way,  wash  the  stained 
portion  of  the  cloth  in  bleaching-powder  to  which  have  been 
added  some  water  and  3  or  4  drops  of  acetic  acid. 


133 


APPENDIX  B 
TABLE  OF  CONSTANTS 

LIST  OF  THE  COMMON  ELEMENTS,  THEIR  SYMBOLS,  AND 
THEIR  ATOMIC  WEIGHTS 


Aluminium 
Antimony  . 
Arsenic  . 
Barium  .     . 
Bismuth 
Boron     .     . 
Bromine 
Cadmium    . 
Calcium .     . 
Carbon  .     . 
Chlorine 
Chromium  . 
Cobalt    .     . 
Copper   .     . 
Fluorine 
Gold  .     .     . 
Hydrogen    . 


0=10 


Al 

27.1 

Iodine       .     .     .     . 

Sb 

120.2 

Iron      

As 

74.96 

Lead    

Ba 

137.37 

Magnesium   . 

Bi 

20S.O 

Manganese    .     .     . 

B 

11.0 

Mercury    .     . 

Br 

79.92 

Nickel      .     . 

Cd 

112.4 

Nitrogen  .     .     .     . 

Ca 

40.07 

Oxygen          .     .     . 

C 

12.00 

Phosphorus  .     .     . 

Cl 

35.46 

Potassium     .     .     . 

Cr 

52.0 

Silicon      .     .     .  .  . 

Co 

58.97 

Cu 

63.57 

Sodium     .     .     .     . 

F 

19.0 

Sulfur       .     .  •  . 

Au 

197.2 

Tin.     .     .   l>.     .     . 

H 

1.008 

Zinc 

I 

126.92 

Fe 

55.84 

Pb 

207.2 

Mg 
Mn 

24.32 
54.93 

Hg 
Ni 

200.6 

58.68 

N 

14.01 

0 

16.00 

P 

31.04 

K 

39.1 

Si 

28.3 

Ag 

Na 

107.88 
23.0 

S 

32.06 

Sn. 

118.7 

Zn 

65.37 

TENSION  OF  AQUEOUS  VAPOR  AT  VARIOUS  TEMPERATURES, 
EXPRESSED  IN  MILLIMETERS  OF  MERCURY 


TEMPERATURE 


PRESSURE      TEMPERATURE 


16° 13.62 

17° 14.4 

18°  .     .     .     .     ...     .  15.46 

19°  .     .     .     .....  16.45 

20°  .   '.  17.51 


PRESSURE 


21° 18.62 

22° 19.79 

23° 21.02 

24° 22.32 

25°  .  23.69 


134 


WEIGHT  IN  GRAMS  OF  1  LITER  OF  VARIOUS  GASES  MEASURED 
UNDER  STANDARD  CONDITIONS 

Acetylene 1.1621  Hydrogen  sulfide      .     .     .  1.5392 

Air 1.2928  Methane 0.7168 

Ammonia.     .     .f    ...     .  0.7708  Nitric  oxide 1.3402 

Carbon  dioxide  ....  1.9768  Nitrogen 1.2507 

Carbon  monoxide   .     .     .  1.2504  Nitrous  oxide 1.9777 

Chlorine 3.1674  Oxygen 1.4290 

Hydrogen 0.08987  Sulfur  dioxide      ....  2.9266 

Hydrogen  chloride .     .     .  1.6398 

THE  METRIC  SYSTEM 

This  system  is  now  used  in  all  civilized  countries  with  four  or 
five  exceptions.  The  United  States  and  Great  Britain  are  among 
the  few  countries  that  have  not  formally  adopted  it,  but  even 
in  these  countries  the  system  is  universally  used  by  scientists  and 
is  coming  into  use  more  and  more  by  manufacturers. 

In  the  metric  system  each  unit  is  10  times  as  large  as  the 
next  lower  unit ;  hence  the  system  is  often  termed  the  "  decimal 
system." 

1.  Length.    The  unit  is  the  meter.   It  is  equal  to  39.37  inches. 

10  millimeters  (mm.)  =  1  centimeter  (cm.) 
10  centimeters  =  1  decimeter  (dm.) 
10  decimeters  =  1  meter  (m.) 
1000  meters  =  1  kilometer  (km.) 

The  only  measures  of  length  ordinarily  used  by  the  chemist 
are  the  millimeter  and  the  centimeter ;  thus,  the  height  of  the 
barometer  at  the  sea  level  is  recorded  as  76  cm.  (or  more  commonly 
as  760  mm.),  and  not  7  dm.  and  6  cm. 

2.  Volume.    The  unit  generally  used  is  the  cubic  centimeter. 

1000  cubic  millimeters  =  1  cubic  centimeter  (cc.) 
1000  cubic  centimeters  =  1  cubic  decimeter  =  1  liter 
1000  cubic  decimeters  =  1  cubic  meter 

The  chemist  uses  only  the  cubic  centimeter  and  the  liter  as 
measures  of  volume.  Thus,  the  volume  of  a  test  tube  is  given  as 
(say)  25  cc. ;  that  of  a  flask  as  (say)  500  cc.,  or  £  liter. 

135 


3.  Weight.  The  unit  is  the  gram.  This  is  approximately  the 
weight  of  1  cc.  of  pure  water  at  its  temperature  of  greatest  den- 
sity (4°).  It  is  equal  to  15.43  grains. 

10  milligrams  (mg.)  =  1  centigram  (eg.) 
10  centigrams  =  1  decigram  (dg.) 
10  decigrams  =  1  gram  (g.) 
1000  grams  =  1  kilogram  (kg.) 

The  gram  and  kilogram  are  the  units  of  weight  most  generally 
used  by  the  chemist.  Thus,  the  weight  of  a  crucible  is  given  as 
(say)  10.532  g.  and  not  10,532  mg.  or  10  g.  5  dg.  3  eg.  2  mg. 

Note  that 

1  pound  troy  =  5760  grains  =  373.24  grams. 
1  pound  avoirdupois  =  7000  grains  =  453.59  grams. 
1  ounce  avoirdupois  =  28.35  grams. 
1  U.  S.  liquid  quart  =  946.36  cubic  centimeters. 


Also  note  that 


1  centimeter  =  nearly  f  inch. 

1  meter  =  nearly  1.1  yards. 
1  kilogram  =  nearly  2£  pounds  avoirdupois. 


im 


• 

irnrTTTni 


TTTTTnT 


10 


TEN-CENTIMETEB  SCALE 


136 


TABLE  OF  SOLUBILITIES  OF  SOME  OF  THE  COMPOUNDS 
OF  THE  METALS 


ACETATE  1. 

BROMIDE 

CARBONATE 

CHLORATE 

CHLORIDE 

CHROMATE 

HYDROXIDE 

IODIDE 

NITRATE 

OXIDE 

PHOSPHATE 

SILICATE 

(ORTHO) 

SULFATE 

SULFIDE 

Aluminium      .     .     . 

W 

W 

W 

W 

A 

W 

W 

A 

A 

A 

W 

A 

Ammonium     .     .     . 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

Barium  

W 

W 

A 

W 

W 

A 

W 

W 

W 

A 

A 

A 

I 

W 

Calcium      .... 

W 

W 

A 

W 

W 

X 

W 

W 

W 

X 

A 

A 

X 

X 

Cobalt    

W 

W 

A 

W 

W 

A 

A 

W 

W 

A 

A 

A 

W 

A 

Copper  

W 

W 

A 

W 

W 

W 

A 

"W 

W 

A 

A 

A 

W 

A 

Ferric    

W 

W 

W 

W 

W 

A 

W 

W 

A 

A 

A 

W 

A 

Ferrous  

W 

W 

A 

W 

W 

A 

W 

W 

A 

A 

A 

W 

A 

Lead      

W 

y 

A 

W 

x 

A 

A 

x 

W 

A 

A 

A 

I 

A 

Magnesium      .     .     . 

W 

W 

A 

W 

W 

W 

A 

W 

W 

A 

A 

A 

W 

A 

Manganese      .     .     . 

W 

W 

A 

W 

W 

W 

A 

W 

W 

A 

A 

A 

W 

A 

Mercuric    .... 

W 

W 

A 

W 

W 

X 

A 

W 

A 

A 

X 

I 

Mercurous  .... 

W 

A 

W 

A 

A 

A 

W 

A 

A 

X 

Nickel    

W 

W 

A 

W 

W 

A 

A 

W 

W 

A 

A 

A 

W 

A 

Potassium  .... 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

Silver     

W 

T 

A 

W 

T 

A 

T 

W 

A 

A 

Y 

A 

Sodium  

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

W 

Stannic  

W 

W 

W 

A 

W 

A 

A 

A 

Stannous    .... 

W 

W 

W 

A 

A 

W 

A 

A 

W 

A 

Zinc  

W 

W 

A 

W 

W 

W 

A 

W 

W 

A 

A 

A 

W 

A 

W,  soluble  in  water. 

A,  insoluble  in  water,  soluble  in  either  HC1  or  HNO3  or  in  both. 

I,  insoluble  in  water  and  in  acids. 

X,  slightly  soluble  in  water  and  slightly  or  readily  soluble  in  acids. 

137 


TREATMENT  OF  CUTS  AND  WOUNDS 

Every  laboratory  should  be  supplied  with  the  materials 
necessary  for  the  treatment  of  cuts  and  burns.  Such  wounds 
when  immediately  and  intelligently  treated  give  little  or  no 
trouble,  but  if  left  to  take  care  of  themselves  infection  may 
occur  and  serious  results  follow.  In  case  of  severe  wounds, 
the  student,  after  the  preliminary  treatment  in  the  laboratory, 
should  be  sent  to  a  physician. 

The  following  materials  required  for  the  treatment  of  wounds 
should  be  kept  in  the  laboratory  in  a  tight  cabinet  or  cupboard  : 

1.  Plain,  sterile  gauze  bandage :   6  rolls,  1  inch  by  10  yards ;  6 
rolls,  2  inches  by  10  yards. 

2.  Adhesive  plaster  for  holding  gauze  in  place :  2  rolls,  0.5  inch 
by  10  yards. 

3.  1000  cc.  of  benzine  (low-boiling  gasoline). 

4.  2000  cc.  of  Seiler's  solution  (this  may  be  made  from  tablets 
purchased  at  any  drug  store). 

5.  Boric  acid  solution  prepared  by  dissolving  20  g.  of  boric  acid 
in  1000  cc.  of  water. 

6.  Iodine  solution  —  ordinary  tincture  of  iodine ;  may  be  purchased 
at  any  drug  store. 

7.  100  cc.  of  Agnew's  solution  prepared  after  the  following  pre- 
scription : 

Tannic  acid    .     .     ......  ...  10  grains 

Borax .     .  .    '.   '..  10  grains 

Glycerine -..•'••     .  .     .     .'  1  drachm 

Camphorated  water      .     i,  -.  •  .  .     .     .  q.s.  to  make  1  ounce 

Different  wounds  should  be  treated  as  follows : 

a.  Cuts  from  glass.   Remove  any  dirt  or  grease  from  the 
wound  and  surrounding  skin  by  washing  with  gauze  saturated 
with  benzine.    A  rather  free  bleeding  at  first  will  help  to  pre- 
vent infection.    Finally  wash  the  wound  with  a  piece  of  gauze 
saturated  with  the  iodine  solution;   then  bandage  so  as  to 
prevent  contamination. 

b.  Burns.   Apply  gauze  saturated  with  Seiler's  solution  and 
then  bandage. 

c.  Burns  from  acids.  Treat  the  same  as  ordinary  burns,  as 
directed  under  b. 

138 


d.  Burns  from  alkalies.   Wash  with  boric  acid  solution  on 
gauze  and  then  bandage. 

e.  Acid  in  eyes.    Wash  the    eyes   with  a  large    volume  of 
water,  then  with  a  solution  of  boric  acid.    Finally  add  a  few 
drops  of  Agnew's  solution  and  apply  to  the  eyes  a  small  gauze 
pad  which  is  kept  saturated  with  ice  water. 

INFORMATION  REGARDING  APPARATUS  AND 
CHEMICALS 

The  lists  following  include  the  apparatus  and  chemicals  re- 
quired for  the  experiments  in  this  notebook.  It  is  always  best 
to  furnish  each  student  with  as  complete  an  outfit  as  possible 
and  to  hold  him  responsible  for  the  same.  Certain  pieces  may, 
however,  be  used  in  common  by  a  number  of  students,  and 
these  have  been  placed  in  a  separate  list.  It  is  always  cheapest 
to  purchase  the  apparatus  and  chemicals  in  as  large  quantities 
as  possible.  The  amounts  of  most  of  the  chemicals  needed  for 
a  class  of  ten  are  so  small  that  the  cost  of  the  same  will  be 
proportionately  much  greater  than  when  larger  quantities  are 
ordered.  It  is  always  best  to  order  the  definite  amounts  of  chem- 
icals listed  in  the  catalogues,  such  as  100  g.  or  1  Ib.  ;  otherwise 
the  cost  of  weighing  out  odd  quantities  and  preparing  these  for 
shipment  may  amount  to  more  than  the  cost  of  the  chemicals.  The 
supplies  may  be  obtained  from  any  of  the  large  dealers.  Cata- 
logues will  be  sent  on  application  and  should  be  in  every  school. 
The  following  are  the  addresses  of  some  of  the  largest  firms : 

Central  Scientific  Company,  412  Orleans  St.,  Chicago,  111. 

Chicago  Apparatus  Co.,  32  Clinton  St.,  Chicago,  111. 

Kauffman-Lattimer  Co.,  Columbus,  Ohio. 

L.  E.  Knott  Apparatus  Co.,  Boston,  Mass. 

Eimer  and  Amend,  205  Third  Avenue,  New  York  City. 

Standard  Scientific  Co.,  70  Fifth  Avenue,  New  York  City. 

Scientific  Materials  Co.,  711-719  Forbes  St.,  Pittsburgh,  Pa. 

Arthur  H.  Thomas  Company,  Philadelphia,  Pa. 

E.  H.  Sargent  &  Co.,  145  Lake  St.,  Chicago,  111. 

C.  H.  Stoelting  Co.,  3037  Carroll  Avenue,  Chicago.  ' 

The  Will  Corporation,  Rochester,  New  York. 

139 


A  list  of  the  supplies  needed  should  be  sent  to  a  number  of 
firms  for  quotations  on  prices.  In  ordering  any  piece  of  appa- 
ratus a  certain  form  in  some  catalogue  should  be  designated ; 
otherwise  it  will  be  impossible  to  compare  the  prices.  In  gen- 
eral it  is  best  to  purchase  as  simple  a  form  of  apparatus  as 
possible ;  for  example,  20  cents  will  buy  a  Bunsen  burner 
which  for  ordinary  purposes  is  preferable  to  those  costing  $1. 
A  much  higher  price  will  have  to  be  paid  for  small  orders 
placed  for  immediate  delivery.  A  person  experienced  in  the 
purchase  of  supplies  will  always  find  it  possible  to  reduce 
materially  the  cost  of  the  order. 

APPARATUS  REQUIRED  FOR  EACH  STUDENT  (TO  BE 
KEPT  IN  STUDENT'S  LOCKER) 

Beakers,  nest  of  7  (100-cc.  to  700-cc.). 

Blowpipe,  mouth. 

Bottle,  narrow-necked,  1000-cc.  (Fig.  25,  £). 

Bottles,  wide-mouthed :  1  (60-cc.)  (Fig.  38,  A)  ;  5  (250-cc.)  (Fig.  20). 

Burner,  wing-top,  for  bending  glass  tubing  (Fig.  4). 

Calcium  chloride  drying-tube,  straight,  15  cm.  in  length  (Fig.  23,  J3). 

Charcoal,  1  piece  8  cm.  x  3  cm. 

Deflagrating-spoon. 

Dish,  lead,  diameter  about  6  cm.,  depth  3  cm. 

Evaporating-dish,  diameter  7  cm. 

File,  round,  about  15  cm.  in  length. 

File,  triangular,  about  15  cm.  in  length. 

Filters,  25,  diameter  about  11  cm. 

Flasks  :  2  (250-cc.)  ;  1  (500-cc.). 

Funnel,  diameter  about  6.5  cm. 

Funnel  tube,  external  diameter  of  tube  6  mm. 

Glass  rod,  diameter  3  mm.,  1  piece  15  cm.  in  length. 

Glass  rod,  1  piece  10  cm.  in  length. 

Glass  tubing,  200  g.,  soft,  external  diameter  6  mm.,  walls  1  mm.  thick. 

Glass  tubing,  hard,  internal  diameter  1  cm.,  1  piece  30  cm.  in  length. 

Glass  tubing,  hard,  internal  diameter  6  mm.,  1  piece  20  cm.  in  length. 

Mortar  (diameter  about  8  cm.)  and  pestle  (both  of  porcelain). 

Pipe-stem  triangle,  for  holding  porcelain  crucible  (Fig.  16). 

Platinum  wire,  small  (No.  28),  8  cm.  long,  for  flame  tests. 

Porcelain  crucible  and  lid,  diameter  about  3.5  cm. 

140 


Retort,  glass-stoppered,  150-cc.  (Fig.  40). 

Rubber  tubing,  internal  diameter  6  mm.,  1  piece  50  cm.  in  length. 

Rubber  tubing  (soft),  pure  gum,  internal  diameter  5  mm.,  1  piece 

60  cm.  in  length,  for  connections,  etc. 
Screw  clamp  (Fig.  19,  A). 
Splints,  wooden  (ordinary  cigar  lighters),  125. 
Sponge. 

Stopper,  rubber,  one-hole,  to  fit  hard-glass  test  tube. 
Stopper,  rubber,  two-hole,  to  fit  wide-mouthed  250-cc.  bottle. 
Stopper,  rubber,  two-hole,  to  fit  wide-mouthed  60-cc.  bottle. 
Stopper,  rubber,  two-hole,  to  fit  1000-cc.  narrow-mouthed  bottle. 
Test  tube,  graduated,  30-cc.,  about  20  cm.  long,  with  0.5-cc.  graduations. 
Test  tube,  hard  glass,  15  cm.  in  length,  diameter  about  1.8  cm. 
Test  tubes,  12,  length  12  cm.,  diameter  about  1.7  cm. 
Test-tube  brush. 
Test-tube  rack. 
Towel. 

Watch  glass,  diameter  about  8  cm. 
Window  glass,  4  pieces  10  cm.  square. 
Wire  gauze,  2  pieces  12  cm.  square. 


APPARATUS  TO  BE  LEFT  ON  EACH  DESK 

Bunsen  burner,  with  75  cm.  of  rubber  tubing  to  fit. 

Clamp,  iron,  large,  for  holding  flasks  and  condensers. 

Iron  tripod  (Fig.  33). 

Pneumatic  trough  (Fig.  21).  The  trough  should  be  about  12  to 
15  cm.  deep,  and  large  enough  to  hold  4  or  5  wide-mouthed  bottles 
(250-cc.).  It  may  be  round  or  rectangular.  A  pan  made  of  granite 
ware  or  an  earthen  crock  serves  well,  or  any  tinsmith  can  readily 
make  suitable  troughs  of  galvanized  iron. 

Ring  stand  and  3  rings. 

REAGENTS  ON  EACH  DESK 

250-cc.  bottles  filled  with  the  reagents  named  below.  The  bottles 
containing  the  sodium  hydroxide  should  have  ordinary  corks,  the 
others  should  be  glass-stoppered. 

Ammonium  hydroxide  (density  0.90). 

Hydrochloric  acid  (density  1.2). 

Nitric  acid  (density  1.4). 

141 


Sodium  hydroxide  solution  (10  g.  in  100  cc.  of  water). 
Sulfuric  acid  (density  1.84). 

GENERAL  APPARATUS  FOR  TEN  STUDENTS 

2  sets  apparatus  for  testing  conductivity  of  solutions  (Fig.  34)  ;  this 
may  be  purchased  of  supply  houses  or  can  easily  be  constructed. 

1  balance,  weighing  from  0.5  g.  to  500  g.,  with  accompanying  weights. 

2  balances,  sensitive  to  1  eg.  and  made  to  carry  a  load  of  100  g. 
1  barometer. 

1  bottle  or  flask,  2000-cc.  (Fig.  47,  A). 

4  burettes,  50-cc.,  graduated  in  0.1  cc.  (Fig.  37). 

5  calcium  chloride  tubes  (Fig.  28,  D). 

5  pieces  cobalt  glass  10  cm.  square  (for  flame  tests). 

4  condensers,  Liebig  (Fig.  26,  B),  with  rubber  tubing  and  large  clamp. 

2  sets  cork-borers  (6  in  a  set). 

2  gross  corks,  best  grades,  sizes  7,  8,  9,  10,  and  12. 

1  cylinder,  glass,  about  30  cm.  in  length  and  4  to  5  cm.  in  width. 

1  cylinder,  graduated,  200-cc. 

1  cylinder,  graduated,  500-cc. 

1  distilling  apparatus  for  preparing  distilled  water. 

2  flasks,   holding    100  cc.    when   filled   to   point   marked   on   neck 

(Fig.  49,  C). 
1  flask,  graduated  to  hold  1000  cc. 

5  pieces  hard-glass  tubing  20  cm.  long  and  15  mm.  internal  diam- 
eter (Fig.  28,  C). 

1  hydrometer,  reading  from  0.900  to  1.000. 
1  magnifying  glass,  small. 

1  microscope,  eyepiece  1  inch,  objective  £  and  |. 

5  thermometers,  graduated  from  —  10°  to  +  150° C. 

2  tubes,  graduated  in  cubic  centimeters,  50  cm.  in  length  and  about 
2  cm.  in  width. 

2  sets  weights,  1  eg.  to  50  g.,  in  covered  wooden  box. 

CHEMICALS  ON  REAGENT  SHELF  (FOR  USE  OF  ALL  STUDENTS) 

The  bottles  containing  solutions  should  be  glass-stoppered. 
Gummed  letters  of  the  alphabet,  of  different  sizes,  may  be 
obtained  at  little  cost  from  any  stationer,  and  these  may  be 
used  in  making  the  labels  for  the  bottles.  If  the  class  is  small, 
bottles  holding  250  cc.  will  ordinarily  serve;  if  the  class  is 

142 


large,  then  it  is  better  to  use  bottles  holding  at  least  500  cc. 
A  few  of  the  reagents,  such  as  limewater,  are  used  so  exten- 
sively that  it  is  better  to  use  a  1000-cc.  bottle.  Distilled  water 
must  be  used  in  making  all  solutions.  A  10%  solution  signifies 
10  g.  dissolved  in  100  cc.  of  water. 

Acetic  acid  (36%). 

Alcohol  (95%). 

Aluminium  sulfate  (10%  solution). 

Ammonium  carbonate  (25  g.  of  the  solid  dissolved  in  70  cc.  of  water 
and  10  cc.  of  ammonium  hydroxide  (density  0.90)  and  the  solution 
diluted  to  100  cc.  with  water). 

Ammonium  chloride  (10%  solution). 

Ammonium  molybdate  solution. 

Ammonium  sulfide  solution. 

Barium  chloride  (10%  solution). 

Borax  (solid). 

Calcium  chloride  (10%  solution). 

Carbon  tetrachloride. 

Chlorine  water  (water  saturated  with  chlorine.  Must  be  freshly  pre- 
pared as  needed). 

Cobalt  nitrate  (5%  solution). 

Copper  sulfate  (10%  solution). 

Disodium  phosphate  (10%  solution). 

Ferric  chloride  (10%  solution). 

Ferric  sulfate  (10%  solution). 

Lead  acetate  (10%  solution). 

Limewater  (saturated  solution  of  calcium  hydroxide). 

Magnesium  sulfate  (10%  solution). 

Manganese  chloride  (10%  solution). 

Mercuric  chloride  (5%  solution). 

Mercurous  nitrate  (10%  solution). 

Oxalic  acid.  Standard  solution  for  Exercise  93.  Prepare  by  dissolv- 
ing exactly  15  g.  c.  p.  oxalic  acid  (C2H2O4  •  2  H2O)  in  1000  cc.  of 
water. 

Phenolphthalein  (1  g.  dissolved  in  200  cc.  of  alcohol). 

Potassium  bromide  (10%  solution). 

Potassium  chromate  (10%  solution). 

Potassium  ferricyanide  (10%  solution). 

Potassium  ferrocyanide  (10%  solution). 

Potassium  hydroxide  (10%  solution). 

143 


Potassium  iodide  (10%  solution). 

Potassium  sulfocyanide  (10%  solution). 

Silver  nitrate  (4%  solution). 

Soap  (1%  solution). 

Sodium  carbonate  (10%  solution). 

Sodium  chloride  (solid). 

Sodium  peroxide  (solid). 

Starch  solution  (prepared  by  rubbing  to  a  paste  4  or  5  g.  of  starch 
with  cold  water,  and  then  adding,  3  or  4  drops  at  a  time  and  with 
stirring,  to  1  liter  of  boiling  water.  Add  also  about  10  g.  of  zinc 
chloride  (this  acts  as  a  preservative).  Mix  thoroughly,  set  the 
mixture  aside,  and  use  the  clear  supernatant  liquid). 

Tartar-emetic  (1%  solution). 

Zinc  acetate  (10%  solution). 


CHEMICALS  REQUIRED  FOR  A  CLASS  OF  TEN 

The  terms  in  parentheses  after  the  names  of  the  chemicals  refer 
to  the  grade  of  materials  to  be  purchased.    The  abbreviation  c.  p. 

signifies  "chemically  pure." 

APPROXIMATE 
AMOUNTS 

Acid,  acetic  (36%)  (c.  p.) 500  g. 

Acid,  formic  (50%) 500  g. 

Acid,  hydrochloric  (density  1.2)  (c.  p.) 2.5  kg. 

Acid,  nitric  (density  1.4)  (c.  p.) 3  kg. 

Acid,  oxalic  (c.  p.) 200  g. 

Acid,  pyrogallic 100  g. 

Acid,  sulfuric  (density  1.84)  (c.  p.) 4  kg. 

Acid,  tannic  (commercial) 100  g. 

Alcohol,  ethyl  (95%) 1  kg. 

Alcohol,  methyl 250  g. 

Alum  (ammonium)  (pure) 500  g. 

Aluminium  (turnings  or  filings) 50  g. 

Aluminium  sulfate  (pure,  crystals) 500  g. 

Ammonium  carbonate  (pure) 100  g. 

Ammonium  chloride  (pure) -. 200  g. 

Ammonium  hydroxide  (density  0.90)  (c.p.)  .  -.     ....  1.5kg. 

Ammonium  mol'ybdate  solution 500  g. 

Ammonium  nitrate  (pure) 100  g. 

Ammonium  sulfate  (commercial) 500  g. 

Ammonium  sulfide  solution 500  g. 

144 


Antimony 30  g. 

Arsenic     ...... 30  g. 

Arsenic  trioxide  (arsenious  oxide)  (commercial)     ....  30  g. 

Barium  chloride  (c.  p.) 100  g. 

Benzene 200  g. 

Bismuth 30  g. 

Bleaching-powder •. 500  g. 

Bone  black ' 250  g. 

I  Borax  (commercial) 500  g. 

Boric  acid  (pure) 100  g. 

Cadmium 25  g. 

Cadmium  chloride  (c.  p.) 25  g. 

Calcium  carbide 500  g. 

Calcium  carbonate  (precipitated) 500  g. 

Calcium  chloride  (fused  or  granular) 1  kg. 

Calcium  fluoride  (fluorspar) 200  g. 

Calcium  hydroxide  (hydrated  lime) 500  g. 

Calcium  sulfate  (plaster  of  Paris) 2  kg. 

Carbon  disulfide  (commercial) 250  g. 

Carbon  tetrachloride  (commercial) 500  g. 

Chloroform 250  g. 

Cobalt  nitrate  (pure) 25  g. 

Copper  (turnings  or  scrap) 250  g. 

*  Copper  foil  (thin) .     ....     .     .     .'.  100  g. 

Copper  nitrate  (pure) 25  g. 

Copper  oxide  (black,  ordinary) 100  g. 

Copper  sulfate  crystals  (c.  p.) 200  g. 

Cottonseed  oil 200  g. 

Dyes  (Bismarck  brown,  fuchsine,  methyl  violet,  malachite 

green,  Congo  red) 10  g.  of  each 

Alizarin  paste  (20%) 100  g. 

Ether,  sulf  uric 500  g. 

Formalin 100  g. 

Gelatin 50  g. 

Glucose  (sirup)  or  Karo  corn  sirup 1  kg. 

Gypsum  (crystals) 200  g. 

Hydrogen  peroxide 200  g. 

Iodine 25  g. 

Iron  chloride  (ferric)  (c.  p.) 100  g. 

Iron  powder  (iron  reduced  by  alcohol) 150  g. 

Iron  sulfate  (ferrous) 200  g. 

Iron  sulfide 1  kg. 

145 


Iron  wire  (picture-frame  wire),  No.  0 25  yds. 

Junket  tablets 10  tablets 

Lead,  red 25  g. 

Lead  acetate  (sugar  of  lead)  (powdered) 200  g. 

Lead  monoxide  (commercial)  .     .  ' 150  g. 

Lead  nitrate  (pure) 50  g. 

Litmus  cubes • 50  g. 

Litmus  paper  —  100  strips  red,  100  strips  blue   .     .     1  tube  of  each 

Magnesium  carbonate  (powdered) •  100  g. 

Magnesium  sulfate  (Epsom  salts) 500  g. 

Magnesium  wire  or  ribbon 25  g. 

Manganese  chloride 50  g. 

Manganese  dioxide  (commercial) 1  kg. 

Marble  (pieces  size  of  a  walnut) 3  kg. 

Mercuric  chloride  (corrosive  sublimate) 25  g. 

Mercuric  nitrate  (c.  p.) 25  g. 

Mercuric  oxide 25  g. 

Mercurous  nitrate  (c.  p.) .    V    .     .     .     .  100  g. 

Mercury 50  g. 

Nickel  nitrate .     .     ....     .     ..    .  25  g. 

Paraffin     .     .     .     .'.,.,  .     .     .     ...     ..'.  .     ...  .     .  ,  .'    .  500  g. 

Phenolphthaleiu .     .    '.     .     .     .     .  25  g. 

Phosphorus "..........  50  g. 

Potassium  bitartrate  (cream  of  tartar)       .     .     .     .     .     .     .  100  g. 

Potassium  bromide  (granular,  pure)      .     .     ...     • '   .     *  50  g. 

Potassium  carbonate  (c.  p.) 50  g. 

Potassium  chlorate  (small  crystals) 500  g. 

Potassium  chloride  (c.  p.) 100  g. 

Potassium  chromate  (pure,  crystals) 100  g. 

Potassium  chromium  sulfate  (chrome  alum) 100  g. 

Potassium  dichromate  (pure)  .  '   £ . 100  g. 

Potassium  f erricyanide  (c.  p.) 100  g. 

Potassium  ferrocyanide  (c.  p.) 100  g. 

Potassium  hydroxide  (sticks,  electrolytic)       .  , 200  g. 

Potassium  iodide  (pure) 50  g. 

Potassium  nitrate  (pure) 200  g. 

Potassium  permanganate  (pure)  .          50  g. 

Potassium  sulfate  (pure,  anhydrous) 200  g. 

Potassium  sulf  ocyanide  (c.  p.)       ....    - 25  g. 

Silver  nitrate 25  g. 

Soda  lime  (granular) 500  g. 

Sodium 100  g. 

146 


Sodium  acetate  (fused) 200  g. 

Sodium  benzoate  (pure) 25  g. 

Sodium  bicarbonate  (baking-soda) 500  g. 

Sodium  carbonate  (pure,  anhydrous) 250  g. 

Sodium  hydrogen  phosphate  (disodium  phosphate)  (c.  p.)     .  100  g. 

Sodium  hydroxide  (sticks,  electrolytic) 1  kg. 

Sodium  nitrate  (pure) .  200  g. 

Sodium  peroxide 200  g. 

Sodium  potassium  tartrate  (Rochelle  salts)  (powdered)    .     .  500  g. 

Sodium  silicate  solution  (water  glass) 1  kg. 

Sodium  sulfate  (crystals) 200  g. 

Sulfur 500  g. 

Tartar-emetic  (potassium  antimonyl  tartrate) 75  g. 

Tin  (granulated) 75  g. 

Zinc  (granulated,  arsenic-free) 1  kg. 

Zinc  (sheet) 200  g. 

Zinc  acetate  (c.  p.) 25  g. 

Zinc  chloride 100  g. 

Zinc  sulfate  (crystals) 100  g. 

NOTE.    This  does  not  include  substances  always  easily  obtained, 

such  as  sugar,  salt,  lard,  lime,  clay,  coal,  cotton,  iron  wire,  calico 
strips,  lead  (pieces  cut  from  lead  pipe),  soap,  kerosene,  gasoline, 
candles,  cardboard,  starch,  cloth,  milk,  vinegar,  butter,  etc. 


147 


r 


36033 


602257 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


